Revert "Build/CMake: Enabled c++11 on gcc for testing purposes."

This reverts commit 0e58f5ad24.

cmake/compiler/gcc/settings.cmake

@@ -22,5 +22,3 @@ if( WITH_COREDEBUG )
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
   message(STATUS "GCC: Debug-flags set (-g3)")
 endif()
-
-SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")