Support to load bitmap v5 header
Add a bmp v5 test image
Merge branch 'sandbox' into fix-for-loading-bmp-v5
Add TGA/TIFF test images
Merge branch 'fix-for-lacking-getopt_long' into feature-long-option
Merge branch 'stb_image' into release-0.21
Merge branch 'feature-long-option' into release-0.21
Merge branch 'fix-for-loading-bmp-v5' into release-0.21
Bump version
Rebuild configure script
Merge branch 'release-0.21' into develop
Mention yaft, as a sixel-featured terminal
Do be sure to rewind in bitmap test, to fix broken GIF loader
Merge branch 'fix-missing-rewinding' into develop

Conflicts:
	converters/stb_image.h
Merge branch 'develop' into stb_image
Add a test GIF image
Merge branch 'stb_image' into release-0.21
Update version
Merge branch 'release-0.21' into release