Rework COPYING installed in /usr/include/xen/, due to several licences

The notice in the COPYING file in "xen/include/public/COPYING" doesn't
really apply to the files that ultimately are been install at
"/usr/include/xen". The issue are headers in the "sys/" subdirectory
that comes from other projects such as Linux or FreeBSD.

The main issue is that there are two headers that have a different
licence than the MIT licence:

- xen-sys/Linux/gntalloc.h (installed as "sys/gntalloc.h") is public
  domain.
- xen-sys/FreeBSD/gntdev.h (installed as "sys/gntdev.h") is BSD-2.

To clarify this, we'll install a COPYING file with a different notice.

Reported-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>

.gitignore

@@ -194,7 +194,6 @@ tools/hotplug/NetBSD/rc.d/xencommons
 tools/hotplug/NetBSD/rc.d/xendriverdomain
 tools/include/acpi
 tools/include/_libxl*.h
-tools/include/xen/*
 tools/include/xen-xsm/*
 tools/include/xen-foreign/*.(c|h|size)
 tools/include/xen-foreign/checker

tools/include/Makefile

@@ -24,7 +24,6 @@ xen-foreign:
 xen-dir:
 	mkdir -p xen/libelf acpi
 	find xen/ acpi/ -type l -exec rm '{}' +
-	ln -s $(XEN_ROOT)/xen/include/public/COPYING xen/
 	ln -s $(XEN_ROOT)/xen/include/public/*.h xen/
 	ln -s $(XEN_ROOT)/xen/include/public/*/ xen/
 	ln -s ../xen-sys/$(XEN_OS) xen/sys

tools/include/xen/.gitignore

@@ -0,0 +1,2 @@
+*
+!COPYING

tools/include/xen/COPYING

@@ -0,0 +1,26 @@
+XEN NOTICE
+==========
+
+This licence applies to all files within this subdirectory ("/usr/include/xen")
+with the exception of "sys/" which may include headers under different
+licences.
+
+=====================================================================
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to
+deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.