build ctypes on Amiga too

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25145 3ad0048d-3df7-0310-abae-a5850022a9f2
dummy GetLastOSerror to make fcl-whatever build, and header cleanup/fixes

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25146 3ad0048d-3df7-0310-abae-a5850022a9f2