Detects and treat links to ebooks as enclosures

Request here : http://forums.cocoaforge.com/viewtopic.php?t=26520&p=138182
OPDS uses a variation of Atom feeds, with acquisition links : http://opds-spec.org/specs/opds-catalog-1-1-20110627/
Treat relative links for enclosures.

Related to http://forums.cocoaforge.com/viewtopic.php?t=26520&p=138182
Merge pull request #275 from barijaona/OPDS

OPDS support
Update autorevision to 1.9.

Also improve readability of driving scripts.
Apparently Vienna has two root commits.
Merge pull request #280 from dak180/topic/build-system

Update autorevision
Add database queue & doTransactionWithBlock method

The goal is to replace beginTransaction and commitTransaction with a routine including queue management.
Managing a queue avoids the risk of having two SQLite transactions getting nested, which is illegal.
Implement the use of the new transaction block routine

Replace calls to beginTransaction and commitTransaction, calls to @synchronized(db).
Slightly modify some transaction borders.
beginTransaction and commitTransaction are private from now
Serialize accesses to sqlDatabase.

The access is serialized through the combination of another queue and dispatch_sync.
Inspired by Brent Simmons’ article <http://www.objc.io/issue-4/SQLite-instead-of-core-data.html> and FMDatabaseQueue.
After fetching a feed, run callback routines asynchronously.
Code cleanup
Prevent lock when deleting folder
Minor optimizations
Restore 32bit compatibility
Systematically close FMResultsSet when they are not needed anymore
Handle file:// URLs

Fix issue #279
Fix sync issue when one deletes articles before marking them read

See <http://forums.cocoaforge.com/viewtopic.php?t=26526> and <http://forums.cocoaforge.com/viewtopic.php?t=26456>
Silence some Xcode warnings
Spanish localization sent by Juan Pablo Atienza Martinez