Default for options.h shouldn't allow "none"

Try to read from /dev/urandom multiple times, take input from extra sources,
and use /dev/random when generating private keys

- rearrange the runopts code for client and server (hostkey reading is needed
  by both (if the client is doing pubkey auth. otherwise....))

--HG--
extra : convert_revision : 5420858803bfff1e27dfe7fa877ba6fdd747e0c5

--HG--
extra : convert_revision : 48946be1cef774d1c33b0f78689962b18720c627

--HG--
extra : convert_revision : cc8a8c49dc70e632c352853a39801089b08149be