osmo-bts consumes the gsm_data_shared.{h,c} files and assumes the
OpenBSC directory layout. Install the files into the specific
sub-directories to make the --with-openbsc=dir option work.
Change-Id: I3da21402dee3d6f1d812b232b0a3f13b8a462d5b
Add openbsc-dev with source and header files necessary for osmo-bts builds.
Max's note: extracted from Debian packaging work into separate commit.
Change-Id: I25f8c639d2dc525ca280a7cd09de3ca6358d2568