Never freeze again.

Put snapshot related floaters always on top of the full screen preview.
Make having multiple running uploads more robust.
Fix infinite recursion when clicking on the bottom 'Snapshot' button
under certain conditions.
Unfreeze time more robust; unfreeze time out of precaution when
starting an upload (if 'Keep open' not checked).
Fixed a bug that caused all callbacks for successful feed uploads to be
ignored.
Merge remote-tracking branch 'singu/master'
Re: 3ea353bef384772ec6b85131898b33a201c7f5e1, fix minimize case to minimize and not steal focus. Also apply to group chats.
Address clang warnings.

* Split off AIThreadSafeBitsPOD, because offsetof may only be used on POD types.
* Added ASSERT_ONLY and ASSERT_ONLY_COMMA
* Removed a few unused class members
* Fixed a bug in AIHTTPReceivedHeaders::equal that more or less only
  compared the length of the headers before :/
Merge remote-tracking branch 'Aleric/master'
Merge remote-tracking branch 'Lirusaito/master'