#21 Extend capabilites of transform REGSUB

[Wim Nelis]

The transform REGSUB is extended to accept the g-modifier, allowing multiple occurances of a substring to be replaced. Most of the other modifiers can be supplied within the regular expression using the (?:...) notation.
The g-modifier in the syntax check is removed, as only a single data alias is allowed in this transform.

[Wim Nelis]

Extend capabilities of transform REGSUB