Log Message:
3.8: When pulling existing .includes of buildlink3 files from the Makefile,
comment them out by default, and add a comment above them indicating that
only *directly* needed dependencies should be in the (edited, final) bl3
file.

This will hopefully encourage folks to reduce the amount of unnecessary bl3
recursion that is rampant in pkgsrc, making many packages "depend" directly
on APIs they never see nor use.