[hybi] [permessage-deflate] Renaming s2c_ and c2s_ prefix to server_ and client_

[Takeshi Yoshino <[e-mail]>]

(Splitting into an independent thread)

Joakim suggested that we should rename them.
http://www.ietf.org/mail-archive/web/hybi/current/msg10201.html
 > Since all websocket communications are initiated by client to server
 > these should just be s/s2c_/server_/g and s/c2s_/client_/g

Initially, I chose these prefixes to make it easy to understand that
they're attributes for each direction by including source and destination
explicitly. But server_ and client_ are not so confusing, too. As these
parameters are request about the peer's output, everyone should understand
X_no_context_takeover and X_max_window_bits as parameters instructing
compressor of X.

If we do this, we should do this right now. I don't have strong opinion
about this change. If there's no objection, I'll take it.