[VOXporter] Add option so VOXporter does not touch at all a prg file

[cpyrgas]

https://www.xsharp.eu/forum/topic?p=33727#p33727

Wolfgang suggests:

Personally I could see several possibilities:

• XPorter recnognizes the end class that is present in the conditional compilation and does not creates a new one
• XPorter recognizes that the module is an external module in VO and optionally takes it "as is" and does nothing
• I could add some statement/comment for XPorter in the module so it leaves it "as is" without changing anything

Probably best solution is to support a special tag (in comment) put in the first line of the file, telling VOXporter not to touch at all the file. Something like

// VXP-NOCHANGE