fix b1447; improve sub set_whitespace_flags

fix b1447; improve sub set_whitespace_flags

This should have been two commits. The first, fix b1447, is just 1 line
and will influence almost no code. The second improves the efficiency
of sub set_whitespace flags, mostly by processing comments faster. It
also fixes a minor problem with marking a sub call for special
formatting when a side comment appears between the sub name and
opening paren (issue c182).