HPCC-10157 DOCS: Language Reference Links

Fix HPCC-10157 DOCS: Language Reference Links
Fixed the TOXML link, by readding the TOXML module
to the Ref guide, and fixed the invalid XML in that module.
Changed INDEX link to point to INDEX_record_Structure

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #4940 from g-pan/H10157-LR-IDs

HPCC-10157 DOCS: Language Reference Links

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>