[msc] Introduce a libmsc.a library

Attempt to split up bsc/msc functionality according to the specs. The
libbsc.a will be responsible for communicating with the BTS, configuring
it, paging, channel allocation and passing layer3 messages in both
ways. libmsc.a will implement the policy and such.
diff --git a/openbsc/tests/sms/Makefile.am b/openbsc/tests/sms/Makefile.am
index 23df871..2cb37b4 100644
--- a/openbsc/tests/sms/Makefile.am
+++ b/openbsc/tests/sms/Makefile.am
@@ -2,4 +2,4 @@
 noinst_PROGRAMS = sms_test
 
 sms_test_SOURCES = sms_test.c
-sms_test_LDADD = $(top_builddir)/src/libbsc.a -ldl -ldbi
+sms_test_LDADD = $(top_builddir)/src/libbsc.a $(top_builddir)/src/libmsc.a -ldl -ldbi