Change kgdb_parse() to use wrapped versions of parse_expression() and

Change kgdb_parse() to use wrapped versions of parse_expression() and
evaluate_expression() so that any errors are caught and cause the function
to return to 0.  Otherwise the errors posted an exception (via longjmp())
that aborted the current operation.  This fixes the kld handling for
older kernels (6.x and 7.x) that don't have the full pathname stored in
the kernel linker.

MFC after:	3 days