Fix warnings

This change fixes Cosmopolitan so it has fewer opinions about compiler
warnings. The whole repository had to be cleaned up to be buildable in
-Werror -Wall mode. This lets us benefit from things like strict const
checking. Some actual bugs might have been caught too.

libc/sock/inet_ntop.c

@@ -32,8 +32,8 @@
  */
 const char *inet_ntop(int af, const void *src, char *dst, uint32_t size) {
   char *p;
-  unsigned char *ip;
   int i, t, a, b, c, d;
+  const unsigned char *ip;
   p = dst;
   if (!size) return dst;
   if ((ip = src)) {