Fix broken submodules

Following e842fdd25fd6c51c511596571f26c6566f83fa29, disposable and
securimage submodules were broken. This restores them to their previous
state.
Remove reference to ERROR_TWITTER_NO_CURL_EXT from language files

Causes SYSTEM NOTICE: 'Use of undefined constant' errors when using a
language other than English.

Follow-up on commit 5c5ee47bd0d853607f30ccefda8614109abda209
Merge pull request #48 from mantisbt/master

pull updates from origin master