HPCC-11604 Handle escaped capitalization in makeXPathLName

HPCC-11770 introduced a regression when dealing with logical
filenames with escaped capitalization.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #6154 from jakesmith/hpcc-11604

HPCC-11604 Handle escaped capitlization in makeXPathLName

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>