CMakeLists: Fixed GLEW include var name, compile flag vars

After adding FindGLEW.cmake to externals, the variable call for the GLEW include path needed to be revised.
Append flags on OSX, rather than overwrite them.
I realized that GCC_COMPILE_FLAGS was changed to CMAKE_CXX_FLAGS mistakenly, so both were changed to a more platform-independent name.

CMakeLists.txt

@@ -2,12 +2,12 @@ cmake_minimum_required(VERSION 2.6)
 
 project(citra)
 
-SET(CMAKE_CXX_FLAGS "-std=c++11 -fpermissive")
+SET(CXX_COMPILE_FLAGS "-std=c++11 -fpermissive")
 
 # silence some spam
 add_definitions(-Wno-attributes)
 add_definitions(-DSINGLETHREADED)
-add_definitions(${GCC_COMPILE_FLAGS})
+add_definitions(${CXX_COMPILE_FLAGS})
 
 # dependency checking
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/externals/cmake-modules/")
@@ -21,14 +21,14 @@ pkg_search_module(GLFW REQUIRED glfw3)
 # corefoundation is required only on OSX
 IF (APPLE)
     FIND_LIBRARY(COREFOUNDATION_LIBRARY CoreFoundation)
-    SET(CMAKE_CXX_FLAGS "-stdlib=libc++")
-    SET(CMAKE_EXE_LINKER_FLAGS "-stdlib=libc++")
+	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
+	SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++")
 ENDIF (APPLE)
 
 #external includes
 include_directories(${GLFW_INCLUDE_DIRS})
 include_directories(${OPENGL_INCLUDE_DIR})
-include_directories(${GLEW_INCLUDE_DIR})
+include_directories(${GLEW_INCLUDE_PATH})
 
 # workaround for GLFW linking on OSX
 link_directories(${GLFW_LIBRARY_DIRS})