util: rename _windows_reserved_filenames and _windows_reserved_chars

opener: rename _can_symlink to _cansymlink

patch: make patch()/internalpatch() always update the dirstate

patch: move updatedir() from cmdutil into patch Also, create an artificial wdutil.py to avoid import cycles between patch.py and cmdutil.py.

record: unconditionally update the working dir after patching

mq: explicitly updatedir() even if patch() fails It already works that way in practice, and we intend to merge updatedir() into patch().

mq: allow to qpop/push with a dirty working copy (issue2780) It's safe to do so if the sets of changed files in the working copy and patches are disjoint.