partially fix amd64 build on windows

Quality of this commit is questionable. I have no idea whether what I did
here makes sense or not.
But it compiles and runs (provided with hlsdk-xash3d amd64 build, which
is another story).

This omits necessary waf changes that are necessary to make a valid
64-bit build. Apparently it's not enough to just pass `-8` on Windows,
you also need to hack wscript to add `x64` target to MSVC. I'll do that
later when I figure out how.

This change is a precursor for RTX Vulkan effort --
VK_KHR_ray_tracing_pipeline and friends are only available on 64-bit
nvidia drivers (no idea about AMD, pls send GPUs onegai).

engine/common/filesystem.c

@@ -324,7 +324,7 @@ static void listdirectory( stringlist_t *list, const char *path, qboolean lowerc
 #if XASH_WIN32
 	char pattern[4096];
 	struct _finddata_t	n_file;
-	int		hFile;
+	intptr_t		hFile;
 #else
 	DIR *dir;
 	struct dirent *entry;