remove pgrminclude?

I propose to remove the pgrminclude scripts and annotations. AFAICT,
per git log, the last time someone tried to do something with it was
around 2011. Also, many (not all) of the "pgrminclude ignore"
annotations are of a newer date but seem to have just been copied around
during refactorings and file moves and don't seem to reflect an actual
need anymore.

I think the include-what-you-use tool that I've been using lately is a
better tool and can adequately replace pgrminclude.

I'm sending separately a patch to add some IWYU annotations, but these
don't seem to correspond very strongly to pgrminclude annotations, so I
don't see any value in keeping the old ones even for a transition.

Here are the scripts to remove:
1. pgcheckdefines -- This could still be useful???
2. pgcominclude -- redundant with headerscheck
3. pgdefine -- used internally only
4. pgfixinclude -- Could still be useful principle?
5. pgrminclude -- obsolete