tests: add some testing for patch.diffstat()

bdiff: normalize the diff (issue1295) When the common part of a diff can be moved forward, move it forward. Otherwise we don't get deterministic results (it would depends on the way we split for the recursion). That way we get identical hunks when doing the same change, it helps to solve issue1295 (inconsistent diffs on different side during a merge).

merge with crew

hgweb: cleanup the manifest generation

convert: make built-in cvsps the default Reviewed by Frank Kingswood <frank@kingswood-consulting.co.uk>

merge with crew

dirstate.walk: skip unreadable directories (issue1213) Do not abort on permission denied error, just skip the directory.

osutil.c: refactor argument parsing, allow skip=None being passed

convert: fix builtin cvsps under Windows Drafted and reviewed by Frank Kingswood <frank@kingswood-consulting.co.uk>.

dirstate._dirs: fix refcounting broken by 7dfac37cfabf reported by Patrick Waugh