Core/Build: Enable Clang PCH support and OS X specific features

Core: Fix warnings here and there

cmake/compiler/clang/settings.cmake

@@ -0,0 +1,15 @@
+# Set build-directive (used in core to tell which buildtype we used)
+add_definitions(-D_BUILD_DIRECTIVE='"$(CONFIGURATION)"')
+
+if(WITH_WARNINGS)
+  set(WARNING_FLAGS "-W -Wall -Wextra -Wwrite-strings -Winit-self -Woverloaded-virtual -Wfatal-errors")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${WARNING_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${WARNING_FLAGS}")
+  message(STATUS "Clang: All warnings enabled")
+endif()
+
+if(WITH_COREDEBUG)
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g3")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
+  message(STATUS "Clang: Debug-flags set (-g3)")
+endif()