Backport 20156 fix (stack corruption)

Fixes: debbugs:20156

* src/fontset.c (fontset_pattern_regexp): Backport: Replace + 1 with
+ 3 in alloca (tiny change)

src/ChangeLog

+2015-03-22  John F Carr <jfc@mit.edu>
+
+	* fontset.c (fontset_pattern_regexp): Backport: Replace + 1 with
+	+ 3 in alloca (Bug#20156) (tiny change)
+
 2015-03-12  Glenn Morris  <rgm@gnu.org>
 
 	* frame.h (x_set_bitmap_icon): Don't set the icon if icon-type is

src/fontset.c

@@ -1097,9 +1097,9 @@ fontset_pattern_regexp (Lisp_Object pattern)
 	 we convert "*" to "[^-]*" which is much faster in regular
 	 expression matching.  */
       if (ndashes < 14)
-	p1 = regex = alloca (SBYTES (pattern) + 2 * nstars + 2 * nescs + 1);
+	p1 = regex = alloca (SBYTES (pattern) + 2 * nstars + 2 * nescs + 3);
       else
-	p1 = regex = alloca (SBYTES (pattern) + 5 * nstars + 2 * nescs + 1);
+	p1 = regex = alloca (SBYTES (pattern) + 5 * nstars + 2 * nescs + 3);
 
       *p1++ = '^';
       for (p0 = SDATA (pattern); *p0; p0++)