STYLE: add a comment about SetLanguageEnabled()

-add a Generic.cmake for target platforms without operating system

Alex

Modules/Platform/Generic.cmake

@@ -0,0 +1,8 @@
+# This is a platform definition file for platforms without
+# operating system, typically embedded platforms.
+# It is used when CMAKE_SYSTEM_NAME is set to "Generic"
+#
+# It is intentionally empty, since nothing is known 
+# about the platform. So everything has to be specified
+# in the system/compiler files ${CMAKE_SYSTEM_NAME}-<compiler_basename>.cmake
+# and/or ${CMAKE_SYSTEM_NAME}-<compiler_basename>-${CMAKE_SYSTEM_PROCESSOR}.cmake

Source/cmGlobalGenerator.cxx

@@ -534,6 +534,13 @@ const char* cmGlobalGenerator::GetLanguageFromExtension(const char* ext)
   return 0;
 }
 
+/* SetLanguageEnabled() is now split in two parts:
+at first the enabled-flag is set. This can then be used in EnabledLanguage()
+for checking whether the language is already enabled. After setting this
+flag still the values from the cmake variables have to be copied into the
+internal maps, this is done in SetLanguageEnabledMaps() which is called
+after the system- and compiler specific files have been loaded.
+*/
 void cmGlobalGenerator::SetLanguageEnabled(const char* l, cmMakefile* mf)
 {
   this->SetLanguageEnabledFlag(l, mf);