Pull up the following revisions, requestes by christos in ticket #881:

share/mk/bsd.sys.mk revision 1.280, 1.281

Create NETBSDOBJDIR to handle MAKEOBJDIRPREFIX, since that prepends the
prefix to the whole path.
Mention that we cannot handle MAKEOBJDIR

-

Handle more objdir variations for MKREPRO (untested)

(martin)