sr: Finish oemlock support

 * Conditially compile support based on TARGET_HAVE_OEMLOCK.
 * Use liboemunlock for device specific support.

Change-Id: I3cff532812bbb2dde1e20d6987aed31ca4da53cd
sr: Handle back in update_directory

This prevents a segfault when swiping back while browsing files.

Change-Id: I82fef192e2b17d3c84ad10821e925d8b12dcc28e
Merge "sr: Finish oemlock support" into cm-11.0