[PATCH] Add XMLText function (SQL/XML X038)

Hi,

This small patch proposes the implementation of the standard SQL/XML 
function XMLText (X038). It basically converts a text parameter into an 
xml text node. It uses the libxml2 function xmlEncodeSpecialChars[1] to 
escape possible predefined entities.

This patch also contains documentation and regression tests.

Any thoughts?

Best, Jim

1 - 
https://gnome.pages.gitlab.gnome.org/libxml2/devhelp/libxml2-entities.html#xmlEncodeSpecialChars