Baby steps to a release.
Update ChangeLogs.

I looked at every commit since 2.10.7 and I believe I've added everything
that users might care about.
Fix ChangeLog typo.
HTTP: fix some clang warnings
Keyring: fix clang warnings
Gadu-Gadu: fix clang warnings
Merge from release-2.x.y branch. Manually resolved minor conflict in ChangeLog.
Prefer https pidgin.im rather than http
Prefer https over http.

(The commit message for my previous commit was wrong. Should have been
"prefer without www" or something)
Fix links.
Update function name in a comment
Get chat conversation ID only once in common_send
Fix sending of typing state
Fix a crash when using hidden conv window (for persistent chats) and a single compilation error
Fix documentation for purple_utf8_strcasecmp
Oops, changed the wrong param in previous commit
Update debug categories for new filenames
Make purple_prefs_update_old private
Move (_)purple_account_to_xmlnode to internal.h