Compilation fixes for MinGW32

Core/Contents/Include/PolyGlobals.h

@@ -40,10 +40,14 @@ THE SOFTWARE.
 	#pragma warning(disable:4018)
 	#pragma warning(disable:4996)
 	#pragma warning(disable:4309)
+	#ifndef NULL
 	#define NULL 0
+	#endif
 	// Prevent windows.h includes from generating min/max macros that
 	// clash with the templates in <algorithm>
+    #ifndef NOMINMAX
 	#define NOMINMAX
+    #endif
 
 
 #endif

Core/Contents/Source/PolyWinCore.cpp

@@ -168,7 +168,7 @@ void Win32Core::warpCursor(int x, int y) {
 unsigned int Win32Core::getTicks() {
 	LARGE_INTEGER li;
 	QueryPerformanceCounter(&li);
-	return unsigned int(li.QuadPart / pcFreq);
+	return (unsigned int)(li.QuadPart / pcFreq);
 }
 
 void Win32Core::Render() {