+ implemented dos.Keep for i8086-msdos; simple dos TSRs now work

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24730 3ad0048d-3df7-0310-abae-a5850022a9f2
  * fixed compilation after r24661 (added dummy overloads for newly
    implemented LOC_MMREGISTER hlcgobj methods)

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24731 3ad0048d-3df7-0310-abae-a5850022a9f2