CA-129333: Improve debugging for snapwatchd. Add documentation for xslib wrapper.

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>

(cherry picked from commit 80f2bf6ecc2cc6dfd58e316b9dbefe1563537fbf)

Imported-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>