Avoid crash
Issue #5: Completion of error handling
Merge branch 'fix-issue-5' into release-1.1
Update version
Merge pull request #4 from mattn/avoid-crash

Avoid crash
Fix for some environment missing "getopt_long"
Merge remote-tracking branch 'origin/hotfix-for-env-missing-getopt_long' into release-1.1
Fix Issue #6: Remove unnecessary null pointer checks
Merge branch 'fix-issue-6' into release-1.1

Conflicts:
	converters/img2sixel.c
Fix a regression bug introduced by 0221665
Merge branch 'fix-issue-6' into release-1.1
Merge branch 'develop' into release-1.1
Fix a compile error
Fix a compile error
Merge branch 'fix-issue-6' into release-1.1
Merge branch 'release-1.1'
Change the behavior of sixel_dither_set_diffusion_type, improvement for sdump.
Print short usage explanation if invalid option is given.
Issue #7: correct wrong CLEANFILES definition
Issue #7: Add test.log to CLEANFILES