It IMO makes sense to compress large and rarely viewed doc files like 
change logs. This seems to be common practice on Debian etc.

With current cygport, the following results in ChangeLog and 
ChangeLog.gz in the docdir:

src_install()
{
   ...
   dodoc ChangeLog
   gzip -9 -n "${D}/usr/share/doc/${PN}/ChangeLog"
}

The attached patch fixes this and also adds some missing documentation.

-- 
Regards,
Christian