Incompatible pointer types are actually errors (in the sense
that they are invalid C).  Compilers have merely tolerated them as
warnings for backwards compatibility.  This is changing with Clang 16
and GCC 14, so relax the check a little.

Submitted upstream: <https://github.com/fvwmorg/fvwm/pull/100>

diff --git a/configure.ac b/configure.ac
index cd73b925dc077141..974c2c0ed6a70b0f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -220,9 +220,8 @@ AC_MINIX
 
 # catch -Werror and similar options when running configure
 AC_TRY_COMPILE([#include <stdio.h>],
-[int i; int *p; char *c;
-  switch (*p = p = *c) { case 0: printf("%Q", c, p); }
-  *c = &i; c = p;
+[int unused; int *p; char *c;
+  printf("%Q", c, p);
   while (1 || (unsigned int)3 >= 0 || ((int)-1) == ((unsigned int)1));
 ], , AC_MSG_ERROR("
 configure is not able to compile programs with warnings.  Please