Problem: Regexp debug logs don't have a good name.
Solution: Use clear names and make it possible to write logs for the old and
new engines separately. (Taro Muraoka)
Problem: Compiler warnings on 64 bit Windows.
Solution: Add type casts. (Mike Williams) Also fix some white space and
uncomment what was commented-out for testing.
Problem: Syntax highlighting can be slow.
Solution: Include the NFA regexp engine. Add the 'regexpengine' option to
select which one is used. (various authors, including Ken Takata,
Andrei Aiordachioaie, Russ Cox, Xiaozhou Liua, Ian Young)
