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.

tool/build/lib/demangle.c

@@ -47,7 +47,7 @@ void SpawnCxxFilt(void) {
     if (!(g_cxxfilt.pid = vfork())) {
       dup2(pipefds[1][0], 0);
       dup2(pipefds[0][1], 1);
-      execv(path, (char *const[]){cxxfilt, NULL});
+      execv(path, (char *const[]){(char *)cxxfilt, 0});
       abort();
     }
     g_cxxfilt.reader = pipefds[0][0];
@@ -87,7 +87,7 @@ char *DemangleCxxFilt(char *p, size_t pn, const char *s, size_t sn) {
   if (!g_cxxfilt.pid) SpawnCxxFilt();
   if (g_cxxfilt.pid == -1) return NULL;
   buf[0] = '\n';
-  iov[0].iov_base = s;
+  iov[0].iov_base = (void *)s;
   iov[0].iov_len = sn;
   iov[1].iov_base = buf;
   iov[1].iov_len = 1;