Merge branch 'jh/p4-rcs-expansion-in-bytestring'

The RCS keyword substitution in "git p4" used to be done assuming
that the contents are UTF-8 text, which can trigger decoding
errors.  We now treat the contents as a bytestring for robustness
and correctness.

* jh/p4-rcs-expansion-in-bytestring:
  git-p4: resolve RCS keywords in bytes not utf-8
  git-p4: open temporary patch file for write only
  git-p4: add raw option to read_pipelines
  git-p4: pre-compile RCS keyword regexes
  git-p4: use with statements to close files after use in patchRCSKeywords