When you expect a function to return a particular value, don't put a comment
saying that you expect it to return that value and compare it against zero
because it is supposedly faster, for this leads to bugs (especially given the
high rate of sloppy cut'n'paste within ssl3 and dtls1 routines in this
library).

Instead, compare for the exact value it ought to return upon success.

ok deraadt@
Oops, revert changes commited by mistake. The previous commit was supposed
to only apply to s23_srvr.c.
Fix CVE-2014-3506, DTLS handshake message size checks.  From
https://git.openssl.org/gitweb/?p=openssl.git;a=commit;h=1250f12613b61758675848f6600ebd914ccd7636
with comment/whitespace style tweaks

ok bcook@ miod@