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/gsm_04_11_gsup.c b/src/libmsc/gsm_04_11_gsup.c
index 328d047..3566e76 100644
--- a/src/libmsc/gsm_04_11_gsup.c
+++ b/src/libmsc/gsm_04_11_gsup.c
@@ -30,7 +30,7 @@
 #include <osmocom/msc/transaction.h>
 #include <osmocom/msc/msc_common.h>
 #include <osmocom/msc/debug.h>
-#include <osmocom/msc/vlr.h>
+#include <osmocom/vlr/vlr.h>
 #include <osmocom/msc/msub.h>
 #include <osmocom/msc/gsup_client_mux.h>
 #include <osmocom/msc/msc_a.h>