buildlink3.mk changes

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

Hi all,
I've just committed the big patchset to convert buildlink3.mk files to a
somewhat different format, which is smaller and less heavy on the CPU.

If you want to create new buildlink3.mk files, please update
createbuildlink.

If you want to use pkgsrc-wip with pkgsrc-2008Q4, do not update until
you switch to pkgsrc-2009Q1.

If you find a problem, please report it. I can't guaranty a bug slipped
through, given the nature of the change.

Joerg