Both libmsc and libbsc will need distinct gsm0480_send_ussdNotify() and
gsm0480_send_releaseComplete() functions, since there will be distinct
subscriber connection structs.
Rename to msc_send_ussd_notify() and msc_send_ussd_release_complete(), and add
the same in libbsc with bsc_ prefix in new file gsm_04_80_utils.c.
In preparation of this patch, the message generation part of these functions
has been added to libosmocore as gsm0480_create_ussd_notify() and
gsm0480_create_ussd_release_complete(). Use these.
Adjust all libmsc and libbsc callers according to use the msc_* or bsc_*
implementation, respectively.
Change-Id: I33a84e3c28576ced91d2ea24103123431f551173
