Merge branch 'release-0.21'
Merge branch 'develop'
Merge branch 'release'
Merge branch 'release'
Merge branch 'release'
Merge branch 'release'
Merge branch 'release'
Merge branch 'release-0.22'
Merge branch 'check-pkg_config-by-conditional' into build
Merge branch 'release'
Update some LICENSE files
Update the manpage of sixel(5)
Update stb_image.h version to 1.41
Merge branch 'stb_image' into release-0.23
Bump version
Rebuild configure script
Merge branch 'build' into release-0.23
Merge branch 'develop' into release-0.23
Merge branch 'release-0.23' into release
Merge branch 'release'