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/libvlr/vlr.c b/src/libvlr/vlr.c
index e190132..dbf9e67 100644
--- a/src/libvlr/vlr.c
+++ b/src/libvlr/vlr.c
@@ -32,8 +32,8 @@
 #include <osmocom/gsm/gsm48.h>
 #include <osmocom/gsm/ipa.h>
 #include <osmocom/gsupclient/gsup_client.h>
-#include <osmocom/msc/vlr_sgs.h>
-#include <osmocom/msc/vlr.h>
+#include <osmocom/vlr/vlr_sgs.h>
+#include <osmocom/vlr/vlr.h>
 #include <osmocom/msc/debug.h>
 #include <osmocom/msc/gsup_client_mux.h>
 #include <osmocom/msc/paging.h>