res_pjsip: Handle pjsip_dlg_create_uas deprecation

Pjproject has deprecated pjsip_dlg_create_uas in 2.5 and replaced it with
pjsip_dlg_create_uas_and_inc_lock which, as the name implies, automatically
increments the lock on the returned dialog.  To account for this, configure.ac
now detects the presence of pjsip_dlg_create_uas_and_inc_lock and res_pjsip.c
has an #ifdef HAVE_PJSIP_DLG_CREATE_UAS_AND_INC_LOCK to decide whether to use
the original call or the new one.  If the new one was used, the ref count is
decremented before returning.

ASTERISK-25751 #close
Reported-by Josh Colp

Change-Id: I1be776b94761df03bd0693bc7795a75682615ca8