Update FindXenomai.cmake

find_package_handle_standard_args generates all caps variables (XENOMAI_FOUND), while this script is expected to create Xenomai_FOUND.

This changeset creates the appropriately cased variable, but does not unset the all-caps variant for backwards-compatibility reasons (I typically unset it on new modules).
Merge pull request #24 from adolfo-rt/patch-3

Update FindXenomai.cmake