Log Message:
Update to 4.0.1:

Changes from 4.0.0 to 4.0.1
---------------------------

1. The default handling of backslash in sub() and gsub() has been reverted to
   the behavior of 3.1. It was silly to think I could break compatibility that
   way, even for standards compliance.

2. Completed the implementation of Rational Range Interpretation.

3. Failure to get the group set is no longer a fatal error.

4. Lots of minor bugs fixed and portability clean-ups along the way. See
   the ChangeLog for details.