fpmkunit: Amiga, MorphOS and AROS are the AllAmigaLikeOSes

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28559 3ad0048d-3df7-0310-abae-a5850022a9f2
+ implemented tthumbcgarm.g_external_wrapper in a way which does not destroy lr

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28560 3ad0048d-3df7-0310-abae-a5850022a9f2