amiga: reintroduced some of the exec debug functions, which were removed, but actually *DO* exist on classic Amiga and hooked the new SysDebug stuff into the Amiga RTL

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28701 3ad0048d-3df7-0310-abae-a5850022a9f2