MINOR: checks: add rbinary expect match type

MINOR: checks: add rbinary expect match type

The rbinary match works similarly to the rstring match type, however the
received data is rewritten as hex-string before the match operation is
done.

This allows using regexes on binary content even with the POSIX regex
engine.

[Cf: I slightly updated the patch. mem2hex function was removed and dump_binary
is used instead.]