6.0 on Mac OS X 10.3.5.
to use XL C, set PKGSRC_COMPILER=xlc in mk.conf. XLCBASE defaults to
/opt/ibmcmp/vacpp/6.0 (the default installation location on OS X),
this can be overridden in mk.conf too.
this is a work in progress - some simple packages can be built, but
there are still lots of issues that need to be worked through.
