FindVdt.cmake: create imported target and detect version
FindVdt.cmake: create imported target and detect version

Old versions of Vdt (0.4.1 and below) do not export version information,
but ROOT needs 0.4.0 at least, because of the vdt/tanh.h header, so we
deduce the version based on the existence of that header and require the
minimum version that ROOT needs. This file now also creates an imported
target that can be used within ROOT to link against VDT with dependencies
taken care of automatically. Fixes ROOT-9885.

root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,karies/root,karies/root,karies/root,karies/root,karies/root,karies/root,olifre/root,karies/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,olifre/root