patch 8.0.1736: check for C99 features is incomplete

Problem:    Check for C99 features is incomplete.
Solution:   Use AC_PROG_CC_C99 and when C99 isn't fully supported check the
            features we need. (James McCoy, closes #2820)

src/version.c

@@ -762,6 +762,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1736,
 /**/
     1735,
 /**/