Disabled compiler warnings for system headers on MSVC. Removed /Wp64; it's a no-op on VS2013 (our minimum supported version).

GNUmakefile.msvc

@@ -80,7 +80,7 @@ OFILES := $(OFILES:%=$(OBJDIR)/%.o)
 # TODO loads of warnings in the system header files
 CFLAGS += \
 	/Zi \
-	/W4 /Wp64 \
+	/W4 \
 	/wd4100 \
 	/TC \
 	/analyze /bigobj /nologo \

windows/winapi.h

@@ -16,6 +16,10 @@
 #define _WIN32_WINDOWS 0x0600		/* according to Microsoft's pdh.h */
 #define _WIN32_IE 0x0700			/* according to Microsoft's sdkddkver.h */
 #define NTDDI_VERSION 0x06000000	/* according to Microsoft's sdkddkver.h */
+// TODO cl.exe spews garbage warnings for system headers; figure out which flags cause it
+#ifdef _MSC_VER
+#pragma warning(push, 0)
+#endif
 #include <windows.h>
 // Microsoft's resource compiler will segfault if we feed it headers it was not designed to handle
 #ifndef RC_INVOKED
@@ -35,3 +39,6 @@
 #include <d2d1.h>
 #include <float.h>
 #endif
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif