internals: move the bitmanipulation routines into its own file This is to allow more flexibility with the C sources -- now the bitmanipulation routines can be safely imported without importing Python.h

journal: new experimental extension Records bookmark locations and shows you where bookmarks were located in the past. This is the first in a planned series of locations to be recorded; a future patch will add working copy (dirstate) tracking, and remote bookmarks will be supported as well, so the journal storage format should be fairly generic to support those use-cases.