openbsc: Introduce autoconf support to set the OpenBSC include directory
openbsc: Introduce autoconf support to set the OpenBSC include directory

Add autoconf support to set the path to the OpenBSC include directory
so that openbsc/gsm_data_shared.h can be found there.

shimaore/osmo-bts,geosphere/osmo-bts,shimaore/osmo-bts,telenoobie/osmo-bts,shimaore/osmo-bts,shimaore/osmo-bts,osmocom/osmo-bts,geosphere/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts