gplugin/gplugin

Prepare for the 0.31.0 release
v0.31.0
2021-05-27, Gary Kramlich
f25e021e4053
Prepare for the 0.31.0 release

Testing Done:
ran `ninja dist` as well as `ninja all doc test` on the resulting tarball.

Reviewed at https://reviews.imfreedom.org/r/676/
REVIEWBOARD_URL = "https://reviews.imfreedom.org/"
REPOSITORY = "gplugin/gplugin"
REPOSITORY_TYPE = "mercurial"
BRANCH = "default"
LAND_DEST_BRANCH = "default"
LAND_PUSH = False