Fix bug in marshalling doubles on Mac OSX.
Fix bug in marshalling doubles on Mac OSX.

- On OSX, casting a negative double to a uint32_t resulted in a value
  of 0 being transmitted to the server.  Changed the double marshalling
  to cast to an int32_t first.  This needs thorough testing on both
  Linux and OSX.


lees0414/EUproject,mytestbed/oml,mytestbed/oml,lees0414/EUproject,mytestbed/oml,alco90/soml,lees0414/EUproject,alco90/soml,mytestbed/oml,alco90/soml,lees0414/EUproject,mytestbed/oml,lees0414/EUproject,alco90/soml,alco90/soml