* msc/USSD: use more informative names for test cases
* msc/USSD: drop the TC_lu_and_ussd_wrong_code test case
* library/GSUP_Types.ttcn: SS Info IE is optional for GSUP_PROC_SS_*
* library/L3_Templates.ttcn: fix f_facility_or_wc(omit)
* library/SS_Templates.ttcn: add empty Return Result template