FEAT: extended conditional Red/System pragmas (#if, #either) to accept a `contains` operator.

This new operator checks if a given value is present in a given compilation target property. Ex:

    #if legacy contains 'stat32 [...]
FIX: issue #653 (Linux version cannot handle long strings in script header)

Stat64 struct is now used by default for Linux target. Older stat struct is available in the newly added Linux-Old compilation target.