introduce pkg-config files

[Yury G. Kudryashov]

Allen Winter wrote:

> Adding the KDE Buildsystem to this discussion..
> 
> My only concern is that pkg-config files are typically installed in
> locations (like /usr or /usr/local) where the regular user doesn't have
> write-access. Thereby causing problems when installing KDE as a regular
> user.
When you install an autotools package to /home/user/prefix, it installs pkg-
config files to /home/user/prefix/lib/pkgconfig. Then you need export 
PKG_CONFIG_PATH to inform pkg-config about this location.
> 
> But as long as I can still install KDE as my regular user, I don't see any
> reason why not.