Increase length of function name buffer

In xemit.c:xdl_emit_diff() a buffer for showing the function name as
commentary is allocated; this buffer was 40 characters.  This is a bit
small; particularly for C++ function names where there is often an
identical prefix (like void LongNamespace::LongClassName) on multiple
functions, which makes the context the same everywhere.  In other words
the context is useless.  This patch increases that buffer to 80
characters - which may still not be enough, but is better
Signed-off-by: NAndy Parkins <andyparkins@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

xdiff/xemit.c

@@ -118,7 +118,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg) {
 	long s1, s2, e1, e2, lctx;
 	xdchange_t *xch, *xche;
-	char funcbuf[40];
+	char funcbuf[80];
 	long funclen = 0;
 
 	if (xecfg->flags & XDL_EMIT_COMMON)