patch 8.0.1735: flexible array member feature not supported by HP-UX

Problem:    Flexible array member feature not supported by HP-UX. (John
            Marriott)
Solution:   Do not use the flexible array member feature of C99.
diff --git a/src/configure.ac b/src/configure.ac
index 4ae21a1..78023ad 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -36,14 +36,10 @@
 dnl - flexible array member
 AC_MSG_CHECKING(if the compiler can handle Vim code)
 AC_TRY_COMPILE([#include <stdio.h>], [
-  struct with_flexible_member {
-    int count;  // comment
-    char text[]; // another comment
-  };
   enum {
-    one,
-    two,
-    three,
+    one,   // one comment
+    two,   // two comments
+    three, // three comments
   };
   long long int a = 1;
   long long unsigned b = 2;