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.

examples/defer-statements.c

@@ -7,15 +7,15 @@
 │   • http://creativecommons.org/publicdomain/zero/1.0/            │
 ╚─────────────────────────────────────────────────────────────────*/
 #endif
-#include "libc/mem/mem.h"
 #include "libc/mem/gc.h"
+#include "libc/mem/mem.h"
 #include "libc/stdio/stdio.h"
 
 /**
  * Cosmopolitan C is just as awesome as Go!
  * Example contributed by @Keithcat1 (#266)
  */
-main() {
+int main() {
   _defer(printf, "Done!\n");
   for (long i = 0; i < 100000; i++) {
     printf("%i ", i);