Platform: drop unneeded Windowless*Application constructor overloads.

The Configuration class is defined on the Windowless*Context already,
which means it's available at the point where the constructor is defined
and thus there's no need for such workarounds anymore.

src/Magnum/Platform/WindowlessCglApplication.cpp

@@ -109,10 +109,6 @@ WindowlessCglContext::Configuration::Configuration() {
     GL::Context::Configuration::addFlags(GL::Context::Configuration::Flag::Windowless);
 }
 
-#ifndef DOXYGEN_GENERATING_OUTPUT
-WindowlessCglApplication::WindowlessCglApplication(const Arguments& arguments): WindowlessCglApplication{arguments, Configuration{}} {}
-#endif
-
 WindowlessCglApplication::WindowlessCglApplication(const Arguments& arguments, const Configuration& configuration): WindowlessCglApplication{arguments, NoCreate} {
     createContext(configuration);
 }

src/Magnum/Platform/WindowlessCglApplication.h

@@ -390,13 +390,7 @@ class WindowlessCglApplication {
          * alternative.
          * @see @ref WindowlessCglContext
          */
-        #ifdef DOXYGEN_GENERATING_OUTPUT
-        explicit WindowlessCglApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
-        #else
-        /* To avoid "invalid use of incomplete type" */
-        explicit WindowlessCglApplication(const Arguments& arguments, const Configuration& configuration);
-        explicit WindowlessCglApplication(const Arguments& arguments);
-        #endif
+        explicit WindowlessCglApplication(const Arguments& arguments, const Configuration& configuration = Configuration{});
 
         /**
          * @brief Construct without creating the context

src/Magnum/Platform/WindowlessEglApplication.cpp

@@ -686,10 +686,6 @@ WindowlessEglContext::Configuration::Configuration()
     #endif
 }
 
-#ifndef DOXYGEN_GENERATING_OUTPUT
-WindowlessEglApplication::WindowlessEglApplication(const Arguments& arguments): WindowlessEglApplication{arguments, Configuration{}} {}
-#endif
-
 WindowlessEglApplication::WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration): WindowlessEglApplication{arguments, NoCreate} {
     createContext(configuration);
 }

src/Magnum/Platform/WindowlessEglApplication.h

@@ -637,13 +637,7 @@ class WindowlessEglApplication {
          * alternative.
          * @see @ref WindowlessEglContext
          */
-        #ifdef DOXYGEN_GENERATING_OUTPUT
-        explicit WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
-        #else
-        /* To avoid "invalid use of incomplete type" */
-        explicit WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration);
-        explicit WindowlessEglApplication(const Arguments& arguments);
-        #endif
+        explicit WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration = Configuration{});
 
         /**
          * @brief Constructor

src/Magnum/Platform/WindowlessGlxApplication.cpp

@@ -323,10 +323,6 @@ WindowlessGlxContext::Configuration::Configuration() {
     #endif
 }
 
-#ifndef DOXYGEN_GENERATING_OUTPUT
-WindowlessGlxApplication::WindowlessGlxApplication(const Arguments& arguments): WindowlessGlxApplication{arguments, Configuration{}}  {}
-#endif
-
 WindowlessGlxApplication::WindowlessGlxApplication(const Arguments& arguments, const Configuration& configuration): WindowlessGlxApplication{arguments, NoCreate} {
     createContext(configuration);
 }

src/Magnum/Platform/WindowlessGlxApplication.h

@@ -448,13 +448,7 @@ class WindowlessGlxApplication {
          * alternative.
          * @see @ref WindowlessGlxContext
          */
-        #ifdef DOXYGEN_GENERATING_OUTPUT
-        explicit WindowlessGlxApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
-        #else
-        /* To avoid "invalid use of incomplete type" */
-        explicit WindowlessGlxApplication(const Arguments& arguments, const Configuration& configuration);
-        explicit WindowlessGlxApplication(const Arguments& arguments);
-        #endif
+        explicit WindowlessGlxApplication(const Arguments& arguments, const Configuration& configuration = Configuration{});
 
         /**
          * @brief Constructor

src/Magnum/Platform/WindowlessIosApplication.h

@@ -356,13 +356,7 @@ class WindowlessIosApplication {
          * alternative.
          * @see @ref WindowlessIosContext
          */
-        #ifdef DOXYGEN_GENERATING_OUTPUT
-        explicit WindowlessIosApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
-        #else
-        /* To avoid "invalid use of incomplete type" */
-        explicit WindowlessIosApplication(const Arguments& arguments, const Configuration& configuration);
-        explicit WindowlessIosApplication(const Arguments& arguments);
-        #endif
+        explicit WindowlessIosApplication(const Arguments& arguments, const Configuration& configuration = Configuration{});
 
         /**
          * @brief Constructor

src/Magnum/Platform/WindowlessIosApplication.mm

@@ -87,10 +87,6 @@ WindowlessIosContext::Configuration::Configuration() {
     GL::Context::Configuration::addFlags(GL::Context::Configuration::Flag::Windowless);
 }
 
-#ifndef DOXYGEN_GENERATING_OUTPUT
-WindowlessIosApplication::WindowlessIosApplication(const Arguments& arguments): WindowlessIosApplication{arguments, Configuration{}} {}
-#endif
-
 WindowlessIosApplication::WindowlessIosApplication(const Arguments& arguments, const Configuration& configuration): WindowlessIosApplication{arguments, NoCreate} {
     createContext(configuration);
 }

src/Magnum/Platform/WindowlessWglApplication.cpp

@@ -308,10 +308,6 @@ WindowlessWglContext::Configuration::Configuration() {
     #endif
 }
 
-#ifndef DOXYGEN_GENERATING_OUTPUT
-WindowlessWglApplication::WindowlessWglApplication(const Arguments& arguments): WindowlessWglApplication{arguments, Configuration{}} {}
-#endif
-
 WindowlessWglApplication::WindowlessWglApplication(const Arguments& arguments, const Configuration& configuration): WindowlessWglApplication{arguments, NoCreate} {
     createContext(configuration);
 }

src/Magnum/Platform/WindowlessWglApplication.h

@@ -434,13 +434,7 @@ class WindowlessWglApplication {
          * alternative.
          * @see @ref WindowlessWglContext
          */
-        #ifdef DOXYGEN_GENERATING_OUTPUT
-        explicit WindowlessWglApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
-        #else
-        /* To avoid "invalid use of incomplete type" */
-        explicit WindowlessWglApplication(const Arguments& arguments, const Configuration& configuration);
-        explicit WindowlessWglApplication(const Arguments& arguments);
-        #endif
+        explicit WindowlessWglApplication(const Arguments& arguments, const Configuration& configuration = Configuration{});
 
         /**
          * @brief Constructor