adding http2 support (#5628)
adding http2 support (#5628)

Requires nghttp2 libraries
LLNL/spack,matthiasdiener/spack,tmerrick1/spack,mfherbst/spack,krafczyk/spack,lgarren/spack,lgarren/spack,krafczyk/spack,krafczyk/spack,matthiasdiener/spack,mfherbst/spack,LLNL/spack,mfherbst/spack,EmreAtes/spack,mfherbst/spack,lgarren/spack,iulian787/spack,EmreAtes/spack,iulian787/spack,krafczyk/spack,tmerrick1/spack,EmreAtes/spack,matthiasdiener/spack,iulian787/spack,LLNL/spack,tmerrick1/spack,skosukhin/spack,skosukhin/spack,iulian787/spack,tmerrick1/spack,matthiasdiener/spack,skosukhin/spack,skosukhin/spack,iulian787/spack,skosukhin/spack,LLNL/spack,krafczyk/spack,tmerrick1/spack,lgarren/spack,LLNL/spack,lgarren/spack,EmreAtes/spack,matthiasdiener/spack,mfherbst/spack,EmreAtes/spack