Fix Issue #6: Remove unnecessary null pointer checks
Remove original sixel (kmiya's sixel), Mirror repo is now here:
https://github.com/saitoha/sixel
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