Implement more security stuff

- Support deterministic stacks on OpenBSD
- Support OpenBSD system call origin verification
- Fix overrun by one in chibicc string token allocator
- Get all chibicc tests passing under Address Sanitizer

libc/str/pututf16.ncabi.c

@@ -19,6 +19,8 @@
 #include "libc/str/oldutf16.internal.h"
 #include "libc/str/str.h"
 
+/* TODO(jart): DELETE */
+
 /**
  * Encodes character to string as UTF-16.
  *