registry: wrap removing files from the registry in a transaction, closes https://trac.macports.org/ticket/34482
registry: wrap removing files from the registry in a transaction, closes https://trac.macports.org/ticket/34482

When uninstall operations are interuppted manually, this could cause
a problem hard to solve (for end users). See https://trac.macports.org/ticket/34482, "an invalid entry
was passed". Wrapping the deletions in a transaction prevents this,
because the records will either be deleted completely, or not at all.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@100219 d073be05-634f-4543-b044-5fe20cf6d1d6

neverpanic/macports-base,neverpanic/macports-base,danchr/macports-base,macports/macports-base,danchr/macports-base,macports/macports-base