Handle clang compilers properly

CMakeLists.txt

@@ -50,7 +50,8 @@ else()
 endif()
 
 # do this after QScintilla - it generates tons of warnings
-if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
+if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR
+        CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
     set(WARNING_FLAGS "-Wall -Wextra")
     set(CMAKE_CXX_FLAGS "-std=c++0x ${WARNING_FLAGS} ${CMAKE_CXX_FLAGS}")
     set(CMAKE_C_FLAGS "${WARNING_FLAGS} ${CMAKE_C_FLAGS}")