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/msc_a.c b/src/libmsc/msc_a.c
index 59f1a57..97f723c 100644
--- a/src/libmsc/msc_a.c
+++ b/src/libmsc/msc_a.c
@@ -34,7 +34,7 @@
 #include <osmocom/msc/msc_i.h>
 #include <osmocom/msc/paging.h>
 #include <osmocom/msc/signal.h>
-#include <osmocom/msc/vlr.h>
+#include <osmocom/vlr/vlr.h>
 #include <osmocom/msc/transaction.h>
 #include <osmocom/msc/transaction_cc.h>
 #include <osmocom/msc/ran_conn.h>