Undef reallocarray in util.h before declaration

In case we link against the OpenBSD-libc, we want to avoid collisions.

util.h

@@ -26,6 +26,7 @@ void apathmax(char **, size_t *);
 void *ecalloc(size_t, size_t);
 void *emalloc(size_t);
 void *erealloc(void *, size_t);
+#undef reallocarray
 void *reallocarray(void *, size_t, size_t);
 void *ereallocarray(void *, size_t, size_t);
 char *estrdup(const char *);