libxl: include <_libxl_paths.h> in libxl_internal.h

libxl: include <_libxl_paths.h> in libxl_internal.h

Ie, we permit general code in libxl direct access to the manifest
constants such as XEN_RUN_DIR.  This simplifies their use in (eg)
format strings.

This might be controversial because it will make it difficult to make
any of these runtime-configurable later without changing lots of use
sites.  But I don't think it's likely we'll want to do that.

For the moment, leave existing call sites of all the functions in
libxl_paths.c unchanged.  The simplified use arrangements can be used
in new code and when we update call sites for other reasons.

Also correct the dependencies in the Makefile so that _libxl_paths.h
is generated before anything that uses libxl_internal.h.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>