Fix gawk miscompile

See testcase.  Function pointer use was hosed when the destination
function wasn't also called normally by the program.

tests/tests2/42_function_pointer.c

@@ -8,9 +8,13 @@ int fred(int p)
 
 int (*f)(int) = &fred;
 
+/* To test what this is supposed to test the destination function
+   (fprint here) must not be called directly anywhere in the test.  */
+int (*fprintfptr)(FILE *, const char *, ...) = &fprintf;
+
 int main()
 {
-   printf("%d\n", (*f)(24));
+   fprintfptr(stdout, "%d\n", (*f)(24));
 
    return 0;
 }