they contain one to two values and make things harder to understand;
this allows to simplify PLIST_FILES setting and `do-install' target
- Fix `post-patch' target: instead of sed(1)ing each and every file,
and leaving lots of `*.bak' files behind, apply the fix where it is
needed only (while here, simplify that regular expression as well)
- Set correct ALL_TARGET instead blanking it; fix pkg-descr formatting
