nua_subnotref.c, nua_notifier.c, sofia-sip/nua_tag.h, nua_tag.c, nua_params.c, nua_params.h: first refer event may or may not have id parameter. Added parameter nutag_refer_with_id for changing the behaviour (in case something breaks down if id *is* included with first subscription).

test_params.c: added tests for setting and getting NUTAG_REFER_WITH_ID().

test_refer.c: testing Event: refer with and without id.

darcs-hash:20060830133749-65a35-92739849ca90f77da65687f3002b710277a233d3.gz