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.

net/http/escapeurl.c

@@ -45,7 +45,7 @@ char *EscapeUrl(const char *p, size_t n, size_t *z, const char T[256]) {
   if (n == -1) n = p ? strlen(p) : 0;
   if (z) *z = 0;
   if ((q = r = malloc(n * 6 + 1))) {
-    v.p = p, v.n = n;
+    v.p = (char *)p, v.n = n;
     q = EscapeUrlView(r, &v, T);
     if (z) *z = q - r;
     *q++ = '\0';