CMake: use blender_include_dirs("${OPENGL_INCLUDE_DIR}") rather then blender_include_dirs(${OPENGL_INCLUDE_DIR})

Apparently this is needed for MSVC in some cases, reported by Tamito Kajiyama r33895.

CMakeLists.txt

@@ -690,7 +690,7 @@ elseif(WIN32)
 	endif()
 
 	# used in many places so include globally, like OpenGL
-	blender_include_dirs(${PTHREADS_INC})
+	blender_include_dirs("${PTHREADS_INC}")
 
 elseif(APPLE)
 
@@ -946,9 +946,9 @@ endif()
 # Configure OpenGL.
 find_package(OpenGL)
 if(MSVC)
-	include_directories(${OPENGL_INCLUDE_DIR})
+	include_directories("${OPENGL_INCLUDE_DIR}")
 else()
-	blender_include_dirs(${OPENGL_INCLUDE_DIR})
+	blender_include_dirs("${OPENGL_INCLUDE_DIR}")
 endif()
 # unset(OPENGL_LIBRARIES CACHE) # not compat with older cmake 
 # unset(OPENGL_xmesa_INCLUDE_DIR CACHE) # not compat with older cmake