Update with more ports, and improved logic in guile.mk.

Rebase.

Add remaining guile ports; this should now be complete.

Rebase (on 4cec5e5f). Fix some minor issues.

Rebase on 738e4012 and fix:

1. sysutils/mcron somehow got missed out; fix.
2. Add new "conflicts" parameter to update CONFLICTS_BUILD
3. Test all ports for non-clean build and add "conflicts" as needed
4. Centralize some plist variables in guile.mk
5. Adjust environment settings to try and maximize the chance that configure scripts will select the right guile version

It seems that a fair number of ports (mostly ones using cmake or meson for building) will not select the correct guile version when not doing a clean build. I have attempted to address this using CONFLICTS_BUILD (to at least give a useful error), but unfortunately it's hard to test this at present since CONFLICTS_BUILD is broken in the framework due to a known bug in pkg(8).

This issue could be solved in one of the following ways:

1. Move the guile-x.y.pc files to GUILE_PKGCONFIG_DIR, so that only the requested version's .pc file can be found.
2. Patch the configure scripts of the affected ports.

So far I have not done either, because (a) some of the affected ports don't build outside a clean environment anyway (e.g. mail/mailutils, which breaks in the presence of gnuradius), and (b) moving the .pc files to a non-default location other than when strictly needed is rather hostile to building software altogether outside of the ports framework. However I am open to argument on this point.

At this point I believe I have no further changes to make unless I discover a problem in my own work or issues are reported on this review.

Rebase (on de1bf48ce).

Rebase (on c8adede0fca)

Centralize definition of info, docs and examples paths (based on experience of adding a new port with examples)

Disuse USE_LDCONFIG in graphics/guile-cairo based on an IRC discussion with bapt

Re-add lang/guile as a metaport that simply symlinks to the default version, based on IRC discussion with fuz

Pick up CHANGES, MOVED, and finalized PORTREVISION changes from fuz' repo.

Fix off_t bug in guile2 by taking the fix from the guile3 port. This turns out to have been a live bug for mail/mailutils with GUILE enabled on 32-bit platforms, detected by the new compiler strictness. (off_t would have been passed to a function call as the wrong type, possibly leading to garbage values depending on calling convention and file size.) Fix build-stamp issue in passing.