revlog: return offset from _chunkraw()
A subsequent patch will refactor _chunks() and the calculation of the
offset will no longer occur in that function. Prepare by returning the
offset from _chunkraw().
#require test-repo
$ cd "$TESTDIR"/..
New errors are not allowed. Warnings are strongly discouraged.
$ hg files "set:(**.py or **.txt) - tests/**" | sed 's|\\|/|g' |
> xargs python contrib/check-config.py