dissolve libcommon-cs: move gsm48_* code to libmsc, drop sms_next_rp_msg_ref()

Move gsm48_* functions from common_cs.c to libmsc/gsm_04_08.c.

Drop sms_next_rp_msg_ref(), it is just a bunch of bloat around "next_rp_ref++".
Apply the "++" instead, in gsm_04_11.c.

libcommon-cs is now empty, to be removed in subsequent commit.

Change-Id: Ibc410803ce8e273b626124ab9fc934f04df3ae50
3 files changed