Extracted NOMINMAX and WIN32_LEAN_AND_MEAN guards into a proxy header

include/internal/catch_timer.hpp

@@ -15,19 +15,7 @@
 #endif
 
 #ifdef CATCH_PLATFORM_WINDOWS
-#  ifdef CATCH_DEFINES_NOMINMAX
-#    define NOMINMAX
-#  endif
-#  ifdef CATCH_DEFINES_WIN32_LEAN_AND_MEAN
-#    define WIN32_LEAN_AND_MEAN
-#  endif
-#include <windows.h>
-#  ifdef CATCH_DEFINES_NOMINMAX
-#    undef NOMINMAX
-#  endif
-#  ifdef CATCH_DEFINES_WIN32_LEAN_AND_MEAN
-#    undef WIN32_LEAN_AND_MEAN
-#  endif
+#include "catch_windows_h_proxy.h"
 #else
 #include <sys/time.h>
 #endif