* m68k: Fixed damage caused by r27573 and r28177:
  * longjmp: restored loading of function result (d0) which got removed in r28177.
  * While at the point, added test for zero, because longjmp must never return zero values.
  * Assembler reader: 'fp' refers to frame pointer, not the stack pointer.


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28183 3ad0048d-3df7-0310-abae-a5850022a9f2