Remove system.h.

The gyp files already define NOMINMAX and WIN32_LEAN_AND_MEAN.  windows.h
is also included via the D3D includes.

This ends up speeding up the build process significantly by not having
windows.h included in nearly every file.

Also fixes issues on non-windows systems by not having stdarg.h included
in debug.cpp.

Change-Id: Id32d9aac37a5a29df832a062dd8024302a798a1c
Reviewed-on: https://chromium-review.googlesource.com/183251
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/common/debug.cpp b/src/common/debug.cpp
index 523802d..05d3dc6 100644
--- a/src/common/debug.cpp
+++ b/src/common/debug.cpp
@@ -7,7 +7,7 @@
 // debug.cpp: Debugging utilities.
 
 #include "common/debug.h"
-#include "common/system.h"
+#include <stdarg.h>
 
 #if defined(ANGLE_ENABLE_PERF)
 #include <d3d9.h>