library/RSL_Emulation: server mode: handle multiple transceivers

Since change [1], the IPA emulation component allows us to handle
multiple IPA connections, thus multiple RSL connections. The idea
is to attach a TCP/IP connection identifier to each message.

On top of that, this change implements mapping between TCP/IP
connection identifiers and RSL stream identifiers, so we can
finally talk to any of connected transceivers (up to 4 for now),
not only the last connected one (as it was before). The actual
mapping is done during the IPA identification procedure.

Instead of forwarding ASP_IPA_EVENT_UP to a test case, the RSL
emulation component now sends a new event - RSLEM_EV_TRX_UP,
with transceiver number (actually, IPA stream-id) attached.

[1] I93c58c08cf296e5cea81d811650caa1a09b8a579

Change-Id: I86afb55ecc6703ce7a229aaa626223f9331a4778
Related: OS#4546
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 99a8ef9..7d211de 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -192,7 +192,8 @@
 
 	T.start;
 	alt {
-	[] RSL_CCHAN.receive(tr_ASP_IPA_EV(ASP_IPA_EVENT_UP));
+	/* TODO: handle connection events from multiple transceivers */
+	[] RSL_CCHAN.receive(tr_RSLEm_EV(RSLEM_EV_TRX_UP));
 	[] T.timeout {
 		Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Timeout waiting for ASP_IPA_EVENT_UP");
 		}