Move vlr.h & vlr_sgs.h into osmocom/vlr/

Prepare libvlr to be independent, start by moving the vlr headers
into its own directory.

Change-Id: I8b18b05091b35e744b3234d1ce0d537f56bccf07
diff --git a/src/libmsc/ran_peer.c b/src/libmsc/ran_peer.c
index 8604443..09e57eb 100644
--- a/src/libmsc/ran_peer.c
+++ b/src/libmsc/ran_peer.c
@@ -30,7 +30,7 @@
 #include <osmocom/msc/msub.h>
 #include <osmocom/msc/msc_i.h>
 #include <osmocom/msc/msc_a.h>
-#include <osmocom/msc/vlr.h>
+#include <osmocom/vlr/vlr.h>
 #include <osmocom/msc/ran_conn.h>
 #include <osmocom/msc/cell_id_list.h>
 #include <osmocom/msc/msc_vgcs.h>