Pidgin 2.13.0

What's new in this version:

libpurple:
- Unified string comparison
- Properlly shell escape URI's when opening them
- Fix a one byte buffer overread in function purple_markup_linkify
- Fix an issue were utf8 was incorrectly truncated which could lead to
- crashes as we were potentially feeding garbage into glib/gtk.-

libgnt:
- Fixed build against curses 6.0 with opaque structs set
- Fixed a crash when resizing the window

General:
- Fixed bashism in autotools

XMPP:
- Show XEP-0066 OOB URLs in any message, not just headlines
- Fix a user after free
- Removed pipelining from BOSH connections
- Don't try to TLS already secured BOSH connections

IRC:
- Fix "Registration timeout" on SASL auth with InspIRCd servers (and possibly others not based on charybdis/ratbox/ircd-seven)
- Fix issues with plugins that modify outgoing messages (such as the custom PART/QUIT feature of the IRC More plugin)
- Fix IRC buffer handling
- Properly handle AUTHENTICATE as a normal command with server prefix.
- Fix a crash caused by a use after free of the MOTD.
- Fix an out of bounds read in irc_nick_skip_mode.
- Fix a write of a single byte before the start of a buffer in irc_parse_ctcp.-

Pidgin:
- Better support for dark themes
- Fixed IPv6 links by not escaping []'s
- Only write buddy icons to the cache if they're not already cached
- Rejoin persistent chats after reconnect
- Made the WIN32 Transparency plugin work on all platforms
- Ensure search results buttons are labeled
- Fix matching unicode smilies
- Correctly update mute/unmute status when the remote side mutes/unmutes us
- Rework the status icon blinking to not used deprecated API
- Don't allow adding a buddy to protocols that don't have an add_buddy callback

Finch:
- Fix handling of search results

Voice & Video:
- Port backend-fs to newer api for farstream relay-info property