pkg-config: Create and install a pkg-config file

Let automake create the openbsc.pc and then install it
into the pkg-config directory of ${libdir}. This is done
in preparation for the public API that will be added soon.

The advertised include directory will be ${incluedir}/openbsc-1.0
to follow userspace practive from glib/gtk/cairo/freetype2 and
many more.
3 files changed