This removes the calls to Perl_get_context() that get automatically
added to XS code for ancient source code compatibility reasons.
The result is about a ~60K size reduction in the binary (based on
comparing two 64-bit stripped irssi binaries compiled
--with-perl-staticlib).
It's used by CTCP CLIENTINFO to print list of known CTCP commands. Also
added CTCP USERINFO command + /SET ctcp_userinfo_reply.
git-svn-id: http://svn.irssi.org/repos/irssi/trunk@2063 dbcabf3a-b0e7-0310-adc4-f8d773084564
