6786: False detection of index names in Search; make index names case insensitive

6786: False detection of index names in Search; make index names case insensitive

Fixing the regex to detect index names in ccl queries.  Changing loop
structure: looping through the index candidates in the query is faster than
testing every index name with a regex.  Making the index comparison case
insensitive will benefit users misspelling the case of an index; Zebra does not
care about it.  Test the change by searching on a word followed by a : or =
character.  Previously, when that word contained an index name like an or nb,
the search would crash.

Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Perltidied the new block to fix indentation

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>