removed recycling of event object, made events immutable so jvm can optimize things...

removed recycling of event object, made events immutable so jvm can optimize things better. Tested roughly with sampler, 1Gb random file and visualvm: effect very small, negligible if tracking is used (paint phase creates a lot more objects). Server on a separate hardware + several clients might cause slightly different results, but I suspect that the difference would still be negligible.

svn changeset:15566/svn branch:6.5