control_if: Add helper function for 'local execution' of control command

Sometimes (particularly when testing), we may want to parse+execute an
arbitrary control command simply form a string buffer, rather than from
a msgb.  Let's add a helper for that.

Change-Id: Iaca748e0d942bb2a1ee7c2776b37485e1439eb0c
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 352b5a7..ab80c1a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -139,7 +139,7 @@
 oap_oap_test_LDADD = $(top_builddir)/src/gsm/libosmogsm.la $(top_builddir)/src/libosmocore.la
 
 fsm_fsm_test_SOURCES = fsm/fsm_test.c
-fsm_fsm_test_LDADD = $(top_builddir)/src/libosmocore.la
+fsm_fsm_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/ctrl/libosmoctrl.la
 
 write_queue_wqueue_test_SOURCES = write_queue/wqueue_test.c
 write_queue_wqueue_test_LDADD = $(top_builddir)/src/libosmocore.la