add BSSLAP coding for Location Services

BSSLAP: there are APDUs transferred in BSSMAP-LE Connection Oriented
Information messages on Lb between BSC and SMLC.
Add BSSLAP coding for these APDU messages:
- TA Layer3
- TA Request
- TA Response, possibly containing Location Estimate coded in GAD
- Reject
- Reset (for intra-BSS handover during TA Request)
- Abort (for inter-BSS handover)

Add encoding and decoding tests.

Change-Id: I6409c4bcac402dc7626a3afce9081c59cd715fe8
diff --git a/tests/bsslap/bsslap_test.ok b/tests/bsslap/bsslap_test.ok
new file mode 100644
index 0000000..f3199e1
--- /dev/null
+++ b/tests/bsslap/bsslap_test.ok
@@ -0,0 +1,7 @@
+--- test_bsslap_enc_dec
+[0] TA Request: ok
+[1] TA Response: ok
+[2] Reject: ok
+[3] Reset: ok
+[4] Abort: ok
+[5] TA Layer3: ok