Fix T40157: Loading movies larger than 4GB in size fails

Issue was caused by _wstat returning EOVERFLOW error because
of file size didn't fit into stat structure which was using
long datatype.

The idea of this patch is to use _wstat64 and _stat64 structure
which is capable storing 64bit file sizes.

Made it a typedef for stat structure used by BLI_stat function
in order to make code easier to follow and avoid ifdefs all
over the place.

Additionally solved issue with BLI_exists which was wrongly
returning False in cases destination file is larger then 4GB.

source/blender/blenkernel/intern/bpath.c

@@ -210,7 +210,7 @@ static int findFileRecursive(char *filename_new,
 	/* file searching stuff */
 	DIR *dir;
 	struct dirent *de;
-	struct stat status;
+	BLI_stat_t status;
 	char path[FILE_MAX];
 	int size;
 	bool found = false;