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/configure.ac b/configure.ac
index 05bea8a..8170a1f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -234,6 +234,7 @@
     include/osmocom/Makefile
     include/osmocom/msc/Makefile
     include/osmocom/smpp/Makefile
+    include/osmocom/vlr/Makefile
     src/Makefile
     src/libmsc/Makefile
     src/libvlr/Makefile