Add spec reference and set explicit values for enum representing
direction parameter for GPRS encryption.
Change-Id: Iaf1b13da2e889d55cc9dd7516710104dba48c992
Related: OS#1582
This patch moves all GSM-specific definitions to include/osmocom/gsm.
Moreover, the headers in include/osmocore/ have been moved to
include/osmocom/core.
This has been proposed by Harald Welte and Sylvain Munaunt.
Tested with `make distcheck'.
Signed-off-by: Pablo Neira Ayuso <pablo@gnumonks.org>