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/calls/isatty.c

@@ -37,7 +37,6 @@
  * @raise EPERM if pledge() was used without tty
  */
 bool32 isatty(int fd) {
-  int e;
   bool32 res;
   struct winsize ws;
   if (__isfdkind(fd, kFdZip)) {