Pound-signs followed by a lone CRLF should not
raise if require-starting-space is specified.
If require-starting-space is true, *and* either:
- new-lines: disbale, or
- newlines: type: dos
is specified, a line with `#\r` or `#\r\n` should
not raise a false positive.
This commit also uses a Set for O(1) membership testing
and uses the correct escape sequence for the nul byte.
If we find a CRLF when looking for Unix newlines, yamllint
should always raise, regardless of logic with
require-starting-space.
Closes: Issue #171.
512fe17047