Enable several variants for HDF5
Enable several variants for HDF5

+cxx, +fortran: Enable support for the respective languages
+threadsafe: Enable multi-threading

LLNL/spack,TheTimmy/spack,mfherbst/spack,skosukhin/spack,TheTimmy/spack,LLNL/spack,EmreAtes/spack,tmerrick1/spack,lgarren/spack,iulian787/spack,lgarren/spack,matthiasdiener/spack,EmreAtes/spack,tmerrick1/spack,TheTimmy/spack,LLNL/spack,lgarren/spack,matthiasdiener/spack,EmreAtes/spack,skosukhin/spack,matthiasdiener/spack,krafczyk/spack,LLNL/spack,EmreAtes/spack,krafczyk/spack,tmerrick1/spack,matthiasdiener/spack,TheTimmy/spack,mfherbst/spack,krafczyk/spack,iulian787/spack,EmreAtes/spack,iulian787/spack,mfherbst/spack,skosukhin/spack,krafczyk/spack,LLNL/spack,skosukhin/spack,skosukhin/spack,krafczyk/spack,iulian787/spack,mfherbst/spack,iulian787/spack,tmerrick1/spack,lgarren/spack,matthiasdiener/spack,TheTimmy/spack,tmerrick1/spack,mfherbst/spack,lgarren/spack