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)
diff --git a/src/version.c b/src/version.c
index c2fc3f3..aff6c6d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1736,
+/**/
     1735,
 /**/
     1734,