Fixes configure failing to find a working compiler under GCC 15's default
-std=gnu23 (upstream fix: https://gmplib.org/repo/gmp/rev/8e7bb4ae7a18).

Upstream fix is patching `acinclude.m4`, but since in the release tarball
all macros are already expanded to `configure` script, so we're patching
all occurrences of that macro.

--- a/configure
+++ b/configure
@@ -6568,7 +6568,7 @@

 #if defined (__GNUC__) && ! defined (__cplusplus)
 typedef unsigned long long t1;typedef t1*t2;
-void g(){}
+void g(int,t1 const*,t1,t2,t1 const*,int){}
 void h(){}
 static __inline__ t1 e(t2 rp,t2 up,int n,t1 v0)
 {t1 c,x,r;int i;if(v0){c=1;for(i=1;i<n;i++){x=up[i];r=x+1;rp[i]=r;}}return c;}
@@ -8187,7 +8187,7 @@

 #if defined (__GNUC__) && ! defined (__cplusplus)
 typedef unsigned long long t1;typedef t1*t2;
-void g(){}
+void g(int,t1 const*,t1,t2,t1 const*,int){}
 void h(){}
 static __inline__ t1 e(t2 rp,t2 up,int n,t1 v0)
 {t1 c,x,r;int i;if(v0){c=1;for(i=1;i<n;i++){x=up[i];r=x+1;rp[i]=r;}}return c;}