pullup from -current:
>revision 1.612
>date: 2009/12/13 09:10:16;  author: mrg;  state: Exp;  lines: +4 -3
>enable MAKEDIRTARGET to be called with a separate environment,
>called $MAKEDIRTARGETENV, defaulting to nothing.
>----------------------------
>revision 1.611
>date: 2009/12/13 09:01:46;  author: mrg;  state: Exp;  lines: +6 -1
>if BSD_MK_COMPAT_FILE is defined, .include it.

(mrg)