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_08_cc.c b/src/libmsc/gsm_04_08_cc.c
index c27caab..dafb41c 100644
--- a/src/libmsc/gsm_04_08_cc.c
+++ b/src/libmsc/gsm_04_08_cc.c
@@ -48,7 +48,7 @@
 #include <osmocom/msc/mncc_int.h>
 #include <osmocom/abis/e1_input.h>
 #include <osmocom/core/bitvec.h>
-#include <osmocom/msc/vlr.h>
+#include <osmocom/vlr/vlr.h>
 #include <osmocom/msc/msub.h>
 #include <osmocom/msc/msc_a.h>
 #include <osmocom/msc/paging.h>