Introduce libc/mem/tinymalloc.inc

This allocator shaves ~20kb off single-threaded tool programs and is
slightly faster than proper malloc for simple non-demanding programs

tool/build/mv.c

@@ -62,6 +62,8 @@ char linkbuf[PATH_MAX];
 
 void Mv(char *, char *);
 
+#include "libc/mem/tinymalloc.inc"
+
 wontreturn void Die(const char *path, const char *reason) {
   tinyprint(2, path, ": ", reason, "\n", NULL);
   exit(1);