Documentation: support for functionality requiring specific extensions.

Doxyfile

@@ -200,7 +200,8 @@ ALIASES                = \
     "requires_gl33=@xrefitem RequiresGL33 \"Requires OpenGL 3.3\" \"Functionality requiring OpenGL 3.3\"" \
     "requires_gl40=@xrefitem RequiresGL40 \"Requires OpenGL 4.0\" \"Functionality requiring OpenGL 4.0\"" \
     "requires_gl41=@xrefitem RequiresGL41 \"Requires OpenGL 4.1\" \"Functionality requiring OpenGL 4.1\"" \
-    "requires_gl42=@xrefitem RequiresGL42 \"Requires OpenGL 4.2\" \"Functionality requiring OpenGL 4.2\""
+    "requires_gl42=@xrefitem RequiresGL42 \"Requires OpenGL 4.2\" \"Functionality requiring OpenGL 4.2\"" \
+    "requires_extension=@xrefitem RequiresExtension \"Requires extension\" \"Functionality requiring specific OpenGL extension\""
 
 # This tag can be used to specify a number of word-keyword mappings (TCL only).
 # A mapping has the form "name=value". For example adding

doc/RequiredExtensions.dox

@@ -16,6 +16,7 @@ capable of OpenGL 2.1 only).
 - @subpage RequiresGL40
 - @subpage RequiresGL41
 - @subpage RequiresGL42
+- @subpage RequiresExtension
 
 @page RequiresGL30 Functionality requiring OpenGL 3.0
 @page RequiresGL31 Functionality requiring OpenGL 3.1
@@ -24,5 +25,6 @@ capable of OpenGL 2.1 only).
 @page RequiresGL40 Functionality requiring OpenGL 4.0
 @page RequiresGL41 Functionality requiring OpenGL 4.1
 @page RequiresGL42 Functionality requiring OpenGL 4.2
+@page RequiresExtension Functionality requiring specific OpenGL extension
 
 */