add ppx_tools 5.3+4.08.0 for OCaml 4.08
add ppx_tools 5.3+4.08.0 for OCaml 4.08

Version 5.1 is for 4.07
Version 5.3 is for 4.08.

Unfortunately we don't have a version that would work with both
compilers. Opam will pick the right one based on the package
constraints.

Signed-off-by: Edwin Török <c8d178016cbaf8a6ef23c2cbc9db96123c48b7dc@citrix.com>

lindig/xs-opam,xapi-project/xs-opam