Rearrange tag and branch deletions.

The existing tag and branch deletions are rearranged, classified into rough groups to help the review of which tags we actually wish to delete. All those deletions that do not match any tags or branches in current SVN are commented out, as any matching tags or branches left after conversion indicate a reposurgeon bug that should be fixed there; that includes deletions in the filters file of two branches that had been moved in SVN, replaced by commented-out branch deletion commands in gcc.lift.