templater: only recursively evaluate string literals as templates (issue4103)

templater: fix escaping in nested string literals (issue4102) Before the templater got extended for nested expressions, it made sense to decode string escapes across the whole string. Now we do it on a piece by piece basis.

merge with stable

shelve: unshelve using an unfiltered repository when evolve is enabled and a hidden obsolete changeset exists in the repository, the strip during unshelve will fail due to filtered revs. we use an unfiltered repository like to repair.strip to strip the proper nodes.

largefiles: update in two steps, handle interrupted updates better An update would try to fetch any missing largefiles after having updated normal files and standins. That could fail or be interrupted and would leave the working directory in a state where the largefiles not only were missing but also were scheduled for remove ... and where the old largefile was left in place. Instead we now remove old largefiles before starting to download and update missing largefiles.

largefiles: inline _updatelfile, prepare for further refactorings

largefiles: cache largefiles for update, also without printmessage

largefiles: cleanup of printmessage handling - the printed flag was redundant

test-module-imports: skip on Python < 2.6, since ast is new in 2.6

Merge with stable.