libxl: Use libxl__ namespace for internal types

libxl: Use libxl__ namespace for internal types

It's not clear that the namespace rules described in libxl.h are
intended to apply to internal types but I don't see why not.

sed -i -e 's/\<libxl_device\>/libxl__device/g'  tools/libxl/*.[ch]
sed -i -e 's/\<libxl_device_kinds\>/libxl__device_kinds/g'  tools/libxl/*.[ch]
sed -i -e 's/\<libxl_gc\>/libxl__gc/g'  tools/libxl/*.[ch]
sed -i -e 's/\<libxl_gc_owner\>/libxl__gc_owner/g'  tools/libxl/*.[ch]
sed -i -e 's/\<libxl_spawn_starting\>/libxl__spawn_starting/g'  tools/libxl/*.[ch]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>