HPCC-9516 Backslash in doc needs special handling for HTM/CHM docs output

Signed-off-by: RichardTaylorHPCC <richard.taylor@lexisnexis.com>
Merge pull request #4516 from RichardTaylorHPCC/B9516

HPCC-9516 Backslash in doc needs special handling for HTM/CHM docs output

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>