patch 9.1.1611: possible undefined behaviour in mb_decompose()

Problem:  possible undefined behaviour in mb_decompose(), when using the
          same pointer as argument several times
Solution: use separate assignments to avoid reading and writing the same
          object at the same time (Áron Hárnási)

closes: #17953

Signed-off-by: Áron Hárnási <aron.harnasi@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: ConcreteCactus

src/regexp.c

@@ -1722,7 +1722,8 @@ mb_decompose(int c, int *c1, int *c2, int *c3)
     else
     {
 	*c1 = c;
-	*c2 = *c3 = 0;
+	*c2 = 0;
+	*c3 = 0;
     }
 }
 

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1611,
 /**/
     1610,
 /**/