Fix re: and glob: patterns in .hgignore (reported by Brad Schick) relglob: and relre: were already detected for a long time, so I kept this undocumented functionality, especially as it was already tested in test-hgignore.

abort: Failed to parse .../t/.hg/hgrc
File contains no section headers.
file: .../t/.hg/hgrc, line: 1
'invalid\n'