some MorphOS specific defines added

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24682 3ad0048d-3df7-0310-abae-a5850022a9f2
basic Amiga/MorphOS support into ExtractFileDrive

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24683 3ad0048d-3df7-0310-abae-a5850022a9f2