Hunter integration: add package/hunter and reference it in main CMakeLists

package/hunter
├── .gitignore               # ignore HunterGate.cmake
├── HunterFetchDeps.cmake    # Fetch SDL, corrade and glfw
├── HunterGate.cmake         # main hunter scripts (ignored in git)
└── HunterInit.cmake         # entry point

CMakeLists.txt

@@ -49,8 +49,20 @@ endif()
 if(NOT CMAKE_VERSION VERSION_LESS 3.4.0 AND NOT CMAKE_SYSTEM_NAME STREQUAL "Android")
     set(LANG CXX)
 endif()
+
+
+option(HUNTER_ENABLED "Get third parties (Corrade, glfw, SDL2) via hunter " OFF)
+if (HUNTER_ENABLED)
+    set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_LIST_DIR}/package/hunter")
+    include(HunterInit)
+endif()
+
 project(Magnum ${LANG})
 
+if(HUNTER_ENABLED)
+    include(HunterFetchDeps)
+endif()
+
 # Use folders for nice tree in Visual Studio and XCode
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 

package/hunter/.gitignore

@@ -0,0 +1 @@
+HunterGate.cmake

package/hunter/HunterFetchDeps.cmake

@@ -0,0 +1,7 @@
+hunter_add_package(corrade)
+if(WITH_GLFWAPPLICATION)
+    hunter_add_package(glfw)
+endif()
+if(WITH_SDL2APPLICATION)
+    hunter_add_package(SDL2)
+endif()

package/hunter/HunterInit.cmake

@@ -0,0 +1,11 @@
+file(
+  DOWNLOAD
+  https://raw.githubusercontent.com/hunter-packages/gate/master/cmake/HunterGate.cmake
+  ${CMAKE_CURRENT_LIST_DIR}//HunterGate.cmake
+)
+
+include("${CMAKE_CURRENT_LIST_DIR}/HunterGate.cmake")
+HunterGate(
+  URL "https://github.com/pthom/hunter/archive/test-corrade-v2018.10.tar.gz"
+  SHA1 "3415f425f0ff1aa1754b8a2b57c77ba20f5b7bbc"
+)