Use new unix_require_c11() macro

VistaCoreLibs/CMakeLists.txt

@@ -87,14 +87,7 @@ if( NOT VISTACORELIBS_SUPPORT_NATIVE_64BIT_ATOMICS )
 endif( NOT VISTACORELIBS_SUPPORT_NATIVE_64BIT_ATOMICS )
 
 # Enable C++11 for all sub-modules on *NIX systems
-if( UNIX )
-	# check if there is already a c++ flag present
-	if( NOT "${CMAKE_CXX_FLAGS}" MATCHES ".*-std=.+" )
-		message( "c++11 features required - adding compiler flag -std=c++11 to CMAKE_CXX_FLAGS" )
-		set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11" CACHE STRING "Flags used by the compiler during all build types." FORCE )
-	endif()
-endif()
-
+unix_require_c11()
 
 # Standard package config
 vista_configure_cpack( VistaCoreLibs )