C++14 deprecates and C++17 removes functions we use for random sounds.
This makes FastRand() fit the URG interface, and uses the appropriate
function.
Refs #5862
Differential Revision: https://code.wildfiregames.com/D3107
This was SVN commit r24302.
This generally makes this code cleaner and easier to maintain, while
also being more modern and fully tested.
Looked at by: leper
Differential Revision: https://code.wildfiregames.com/D8
This was SVN commit r22029.