Remove libiu here, use the functions from libosmo-ranap instead, by applying
the ranap_ / RANAP_ prefix.
Corresponding change-id in osmo-iuh.git is I6a3f7ad15be03fb94689b4af6ccfa828c25f45c0
To be able to run the msc_vlr tests for RAN_UTRAN_IU without Iu client headers
available, add iu_dummy.h, containing mere function signatures that match
iu_dummy.c and a mostly empty struct ranap_ue_conn_ctx.
Make sure we can build with and without --enable-iu: include osmo-iuh headers
only with --enable-iu.
Change-Id: Ib8c4fcdb4766c5e575618b95ce16dce51063206b
00e82d61ab