* Fix portage.cache.template.database.__getitem__() to validate the _mtime_

* Fix portage.cache.template.database.__getitem__() to validate the _mtime_
  field and raise a CacheCorruption exception if necessary.
* Make _mtime_ and _eclasses_ validation code in portdbapi and mirror_cache()
  assume that these fields are the correct type (otherwise a CacheCorruption
  exeception should be raised earlier).
* Fix the sqlite module to implement _getitem() so that it properly inherits
  __getitem__() _mtime_ and _eclasses_ handling. (trunk r12735)

svn path=/main/branches/2.1.6/; revision=12984