Attempt to fix building using MINGW. Affects #55

Core/timing.c

@@ -1,6 +1,8 @@
 #include "gb.h"
 #ifdef _WIN32
+#ifndef _WIN32_WINNT
 #define _WIN32_WINNT 0x0500
+#endif
 #include <Windows.h>
 #else
 #include <sys/time.h>

Makefile

@@ -4,6 +4,9 @@
 # Set target, configuration, version and destination folders
 
 PLATFORM := $(shell uname -s)
+ifneq ($(findstring MINGW,$(PLATFORM)),)
+PLATFORM := windows32
+endif
 
 ifeq ($(PLATFORM),Darwin)
 DEFAULT := cocoa