Explain why bzip2 has repositories on sourceware.org and gitlab.com.
Change error messages in bzip2 source to request that bugs be reported
to project's gitlab issues page.
Fixup project homepage in various documents to point to gitlab project.
Remove trailing whitespace from a few documents.
Update the Release Checklist.
Add myself as new maintainer.
BZ_SEQUENCE_ERROR can be returned if BZ2_bzDecompress is called after
an earlier call already returned BZ_STREAM_END.
Reported-by: Vanessa McHale <vamchale@gmail.com>
