[Bjørn Forsman:
* use "mkdir -p" instead of "ensureDir" (deprecated)
* place *.pc file in $out/lib/pkgconfig/ (instead of
$out/share/pkgconfig/ which doesn't work)
* prefix commit message with "libid3tag:"
]
* Remove package name
* Start with upper case letter
* Remove trailing period
Also reword some descriptions and move some long descriptions to
longDescription.
I'm not touching generated packages.