Use AC_CHECK_TYPES to check for struct statfs64

* m4/statfs.m4: Remove.
* configure.ac (AC_STATFS64): Remove.
(AC_CHECK_TYPES): Add struct statfs64.
* statfs.c: Replace HAVE_STATFS64 with HAVE_STRUCT_STATFS64.
diff --git a/statfs.c b/statfs.c
index d8583f6..35f8652 100644
--- a/statfs.c
+++ b/statfs.c
@@ -83,7 +83,7 @@
 	return 0;
 }
 
-#ifdef HAVE_STATFS64
+#ifdef HAVE_STRUCT_STATFS64
 static void
 printstatfs64(struct tcb *tcp, long addr)
 {
@@ -197,7 +197,7 @@
 	}
 	return 0;
 }
-#endif /* HAVE_STATFS64 */
+#endif /* HAVE_STRUCT_STATFS64 */
 
 #ifdef ALPHA
 int