include/port directory?

I noticed that when installing postgres the following directory is
formed: ~pgsql/include/port/bsd (presumably the bsd changes with the
port upon which it's compiled). This is created as part of the
following target in src/interfaces/libpq:

beforeinstall-headers:
@if [ ! -d $(HEADERDIR) ]; then mkdir $(HEADERDIR); fi
@if [ ! -d $(HEADERDIR)/port ]; then mkdir $(HEADERDIR)/port; fi
@if [ ! -d $(HEADERDIR)/port/$(PORTNAME) ]; \
then mkdir $(HEADERDIR)/port/$(PORTNAME); fi

However, nothing ever seems to be put into this directory and as far
as I can tell these are the only Makefile lines that reference this
directory in any way.

What is the point if creating it in the first place? Should stuff be
put in there or should the directory disappear?

Cheers,
Brook