patch 7.4.1637

Problem:    Can't build with older MinGW compiler.
Solution:   Change option from c++11 to gnu++11. (Ken Takata)

src/version.c

@@ -748,6 +748,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1637,
 /**/
     1636,
 /**/