tools: move libxenctrl below tools/libs

Today tools/libxc needs to be built after tools/libs as libxenctrl is
depending on some libraries in tools/libs. This in turn blocks moving
other libraries depending on libxenctrl below tools/libs.

So carve out libxenctrl from tools/libxc and move it into
tools/libs/ctrl.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org> (stubdom parts)
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> (python parts)
Acked-by: Wei Liu <wl@xen.org>

MAINTAINERS

@@ -226,7 +226,7 @@ M:	Stewart Hildebrand <stewart.hildebrand@dornerworks.com>
 S:	Supported
 L:	xen-devel@dornerworks.com
 F:	xen/common/sched/arinc653.c
-F:	tools/libxc/xc_arinc653.c
+F:	tools/libs/ctrl/xc_arinc653.c
 
 ARM (W/ VIRTUALISATION EXTENSIONS) ARCHITECTURE
 M:	Stefano Stabellini <sstabellini@kernel.org>