m68k: minor bits, addq/subq works also on address regs, remove reference validity check in a_op_const_ref because we have fixref() later anyway

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27876 3ad0048d-3df7-0310-abae-a5850022a9f2
Fix for Mantis #26123.

pdecobj.pas, object_dec:
  * Always check for genericdef and genericlist and not genericdef and ifnot then genericlist.

+ added test

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27877 3ad0048d-3df7-0310-abae-a5850022a9f2