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.]
diff --git a/include/types/checks.h b/include/types/checks.h
index 36b22fe..d798ae2 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -215,6 +215,7 @@
 	TCPCHK_EXPECT_UNDEF = 0, /* Match is not used. */
 	TCPCHK_EXPECT_STRING, /* Matches a string. */
 	TCPCHK_EXPECT_REGEX, /* Matches a regular pattern. */
+	TCPCHK_EXPECT_REGEX_BINARY, /* Matches a regular pattern on a hex-encoded text. */
 	TCPCHK_EXPECT_BINARY, /* Matches a binary sequence. */
 };