increase buffer size for local SDP

There are a lot of codecs these days, and some clients offer all of
them.  If we run out of space in this buffer our local SDP will get
silently truncated, which will cause a difficult to diagnose error in
Sofia-SIP.

Thanks to Anthony Minessale.

FS-4293 --resolve

src/mod/endpoints/mod_sofia/sofia_glue.c

@@ -375,7 +375,7 @@ void sofia_glue_check_dtmf_type(private_object_t *tech_pvt)
 
 void sofia_glue_set_local_sdp(private_object_t *tech_pvt, const char *ip, switch_port_t port, const char *sr, int force)
 {
-	char buf[2048];
+	char buf[65536];
 	int ptime = 0;
 	uint32_t rate = 0;
 	uint32_t v_port;