Repair bounds-checking runtime

Repair bounds-checking runtime

On this weekend a thought came to me again that tinycc could be used for
scripting. Only its bounds-checking mode turned out to be broken, which
is a pity because bounds-checking is sometimes handy especially for
quickly written scripts.

Since tinycc is one of those small beautiful things, seldomly happening
in our times, I couldn't resist trying to fix it.

Thanks,
Kirill

* bcheck:
  Now btest pass!
  lib/bcheck: Prevent __bound_local_new / __bound_local_delete from being miscompiled
  lib/bcheck: Prevent libc_malloc/libc_free etc from being miscompiled