Sync with Gravatar download code

This includes changes of revision 06643f17caf5adae91f0821b033149131b63c59b and revision e1a942e59bd268846f125fad76b2acf29c39a392.

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Fix resizing the message box when gravatar gets enabled

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Updated libgit2

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>