Proposed fix for issue 177: use of legacy (?) SLOT-DEFINITION accessors.

Fix to the ABCL-specific code for inspecting SLOT-DEFINITION objects.
Latest ABCL seems to export all the required SLOT-DEFINITION accessors
from the MOP package.

I'm sorry; some whitespace fixups crept in, as well. If you merge this patch, and then do diff with -w that should make things clearer.