hipchat: Add basic support for personal oauth tokens
Fixes trac ticket 1265 - see the comments on that ticket for reasons on
why personal tokens and not the usual oauth flow. TL;DR hipchat doesn't
allow third party apps to own oauth client secrets. Instead, those are
generated when the "addon" is "installed" which requires a flow that is
either impossible or too awkward to use in bitlbee.
So, after giving up on the right way and telling the users to manage
tokens the ugly way, what's left to do is easy, just a few tweaks in the
sasl blob and short-circuit most of the actual oauth stuff. I didn't
even bother changing the service struct from google. It's not used.
This also updates the gtalk SASL X-OAUTH2 code to use GStrings instead of
juggling with malloc/strlen/strcpy, and simplifies a bit the way
GStrings are used in the equivalent SASL PLAIN code.
