xdiff: fix a hard crash on Windows

The xdiff case of test-diff-antipatience.t started crashing in the C extension
with 882657a9f768 (with 6a71a5ba666b backported so it compiles).  There are a
few more instances of 'long', but this resolves the crashing.

mercurial/thirdparty/xdiff/xdiffi.c

@@ -342,7 +342,7 b' int xdl_do_diff(mmfile_t *mf1, mmfile_t '
 	 * One is to store the forward path and one to store the backward path.
 	 */
 	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
-	if (!(kvd = (int64_t *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
+	if (!(kvd = (int64_t *) xdl_malloc((2 * ndiags + 2) * sizeof(int64_t)))) {
 
 		xdl_free_env(xe);
 		return -1;

mercurial/thirdparty/xdiff/xprepare.c

@@ -296,9 +296,9 b' static int xdl_prepare_ctx(unsigned int '
 		goto abort;
 	memset(rchg, 0, (nrec + 2) * sizeof(char));
 
-	if (!(rindex = (int64_t *) xdl_malloc((nrec + 1) * sizeof(long))))
+	if (!(rindex = (int64_t *) xdl_malloc((nrec + 1) * sizeof(int64_t))))
 		goto abort;
-	if (!(ha = (uint64_t *) xdl_malloc((nrec + 1) * sizeof(unsigned long))))
+	if (!(ha = (uint64_t *) xdl_malloc((nrec + 1) * sizeof(uint64_t))))
 		goto abort;
 
 	xdf->nrec = nrec;