Fix up headers.
Add decoder structs and functions.
Add encoder structs and functions.
Add help text and argument checking to epaipoke.
Unify the two encoder init functions.
Restructure epaipoke code.
Fix minor problems regarding library source.
Add initial specifications for images, [key]frames.
Add some manually-created sample files for testing.

WARNING: I tried my best to check the files, but there might be a
mistake somewhere. Manual encoding in a hex editor is hard. ;)
Prefer the term "scanline" in keyframe spec.
Define a new type for byte arrays.

This prevents bugs due to char signedness.
Make error checks more explicit.
Add a simple mechanism for reporting error messages.
Regular char type should be used for text strings.
Fix parse length reporting for optional sections.
Merge branch 'master' of github.com:tajjada/epai-file-format

Conflicts:
	lib/checksum.c