patch 8.1.0364: compiler warning in xdiff code

Problem:    Compiler warning in xdiff code. (Yegappan Lakshmanan)
Solution:   Initialize directly.
diff --git a/src/xdiff/xemit.c b/src/xdiff/xemit.c
index 718b3ae..dfc1d51 100644
--- a/src/xdiff/xemit.c
+++ b/src/xdiff/xemit.c
@@ -169,7 +169,9 @@
 	long s1, s2, e1, e2, lctx;
 	xdchange_t *xch, *xche;
 	long funclineprev = -1;
-	struct func_line func_line = { 0 };
+	struct func_line func_line;
+
+	func_line.len = 0;
 
 	for (xch = xscr; xch; xch = xche->next) {
 		xche = xdl_get_hunk(&xch, xecfg);