This contains the final 27.1 release and is ready for review.
- depend on math/gmp
- match upstream by turning CAIRO, HARFBUZZ, and JSON options on and turning MAGICK off by default
- remove OPENMP check for graphics/ImageMagick as the openmp is now included in base
- update EMACS_VER in Mk/Uses/emacs.mk
- bump USES=emacs ports or remove BROKEN for net-im/jabber.el and deskutils/howm, which now build
TODO: Possibly wait for Yuuji to re-test and rename the canna patch from emacs27.0.90-canna-20200308.diff.gz to emacs27.1-canna-202008xx.diff.gz.