dirstate: speed up sorting in findfiles

revlog: pass mode to _supported directly

dirstate: localize a bunch of methods for findfiles

Merge with -stable

posixfile_nt: '+' should allow read access. This fixes unexpected I/O error on committing many files due to cset:8a53b39cd402 (r4902 in crew).

merge: don't forget to update the dirstate for exec bit changes

revlog: avoid some unnecessary seek/tell syscalls

manifest: speed up creation of the manifestdict - fold iteration and rawset into parse - avoid creating extra new strings with [:] where possible - speed up node.bin