Added MAGNUM_TARGET_WEBGL definition.

Treating JavaScript and WebGL as first-class compile target. What the
world had come to :-)

CMakeLists.txt

@@ -150,6 +150,9 @@ if(TARGET_GLES)
         set(MAGNUM_TARGET_GLES3 1)
     endif()
 endif()
+if(CORRADE_TARGET_EMSCRIPTEN)
+    set(MAGNUM_TARGET_WEBGL 1)
+endif()
 if(TARGET_DESKTOP_GLES)
     set(MAGNUM_TARGET_DESKTOP_GLES 1)
 endif()

doc/portability.dox

@@ -43,6 +43,7 @@ If you include @ref Magnum.h, you get these predefined macros:
 -   @ref MAGNUM_TARGET_GLES if targeting OpenGL ES
 -   @ref MAGNUM_TARGET_GLES2 if targeting OpenGL ES 2.0
 -   @ref MAGNUM_TARGET_GLES3 if targeting OpenGL ES 3.0
+-   @ref MAGNUM_TARGET_WEBGL if targeting WebGL
 
 Example usage:
 @code

src/Magnum/Magnum.h

@@ -128,6 +128,20 @@ within standard desktop OpenGL. Implies also @ref MAGNUM_TARGET_GLES.
 */
 #define MAGNUM_TARGET_DESKTOP_GLES
 #undef MAGNUM_TARGET_DESKTOP_GLES
+
+/**
+@brief WebGL target
+
+Defined if the engine is built for WebGL (using Emscripten). WebGL is nearly
+equivalent to OpenGL ES 2.0, thus in most cases you don't need to treat it
+differently, but there are some
+[specific restrictions and features](http://www.khronos.org/registry/webgl/specs/latest/1.0/#6)
+which you might want to be aware of. Implies also @ref MAGNUM_TARGET_GLES and
+@ref MAGNUM_TARGET_GLES2.
+@see @ref CORRADE_TARGET_EMSCRIPTEN, @ref building
+*/
+#define MAGNUM_TARGET_WEBGL
+#undef MAGNUM_TARGET_WEBGL
 #endif
 
 /** @{ @name Basic type definitions

src/Magnum/configure.h.cmake

@@ -29,3 +29,4 @@
 #cmakedefine MAGNUM_TARGET_GLES2
 #cmakedefine MAGNUM_TARGET_GLES3
 #cmakedefine MAGNUM_TARGET_DESKTOP_GLES
+#cmakedefine MAGNUM_TARGET_WEBGL