Code refactor: split defines into separate header, changes to SSE type headers.

I need to use some macros defined in util_simd.h for float3/float4, to emulate
SSE4 instructions on SSE2. But due to issues with order of header includes this
was not possible, this does some refactoring to make it work.

Differential Revision: https://developer.blender.org/D2764

intern/cycles/device/device_cpu.cpp

@@ -48,6 +48,7 @@
 #include "util/util_logging.h"
 #include "util/util_map.h"
 #include "util/util_opengl.h"
+#include "util/util_optimization.h"
 #include "util/util_progress.h"
 #include "util/util_system.h"
 #include "util/util_thread.h"