This patch updates the handling of regular expression matches
in virtual classifications. Previously the matching would stop
if it matched the source value even if there was no matching
date.

If source 'abc' on 2008-01-01 was matched against

  [REGEXP-MAPPINGS]:

  ab.*:2008-02-01:DEST1:1
  a.*:2007-01-01:DEST2:1

it would match "ab.*" but then be rejected (return '{Unmatched}')
because the expression is only valid from 2008-02-01. 

This patch will update the matching so it will continue looking
for valid matches until either a valid match is found or all
possible regular expressions has been tested.

Note that matches are still done in the defined sequence in the 
mapping file. It will always use the first valid match found.