Add libsodium and use it to build zeromq
Addressed issue SPI-1399. Experimental run #2185 was successful (see https://epsft-jenkins.cern.ch/job/lcg_experimental/2185/)
Addressed issue SPI-1399. Experimental run #2185 was successful (see https://epsft-jenkins.cern.ch/job/lcg_experimental/2185/)