libpurple -- multiple vulnerabilities

Pidgin reports:

libpurple
Fix a crash when receiving UPnP responses with abnormally long values.
MXit
Fix two bugs where a remote MXit user could possibly specify a local file
path to be written to.
Fix a bug where the MXit server or a man-in-the-middle could potentially
send specially crafted data that could overflow a buffer and lead to a crash
or remote code execution.
Sametime
Fix a crash in Sametime when a malicious server sends us an abnormally long
user ID.