Added gitignore
- Fixed the ant build script so that it creates the output diretory for the
  .class files if it does not yet exist.
- Added jar files to the gitignore
Added the Android specific UDPMulticastProvider hack so that DatagramPackets are
reset to the maximum size before they are reused for socket.receive().  This
should result in correct behavior for both single and multi-fragment messages on
all versions of Android