[DotGNU]pnetlib compilation changed

[Rhys Weatherley]

I've modified the compilation scripts for pnetlib so that most
of it will compile in normal (non-metadata) mode, except for
the following assemblies, which still have a few cscc-related
errors that need fixing:

    mscorlib.dll
    System.dll
    I18N.CJK.dll

Everything else builds cleanly (whether they work or not is
still an open question - please help with the test suites).

The metadata-only compile is now selected in the csant build
files.  e.g. the following line in "System.build":

    <arg compiler="cscc" value="-fmetadata-only"/>

Commenting out this line will allow you compile the code in
normal mode for testing purposes.

Cheers,

Rhys.