Add the ability to limit the size of log messages

[GoogleCodeExporter]

I recently had an issue where, for whatever reason that I cannot determine, 
an RPC call returned the entire GWT javascript file instead of what it 
would normally return.  GWT then reported this as an exception with the 
getMessage() returning that entire file body.  Then gwt-log logged it and 
sent that back to the server, which crashed because it ran out of memory - 
this was a 12MB log message which had to have some stuff appended and 
prepended so it was copied ten times over.

My suggestion is to add a feature to makes it really easy to limit the size 
of a log message to 32KB, or even just hard-code that.

The reason this should be done inside of gwt-log is that gwt-log takes the 
exception as a parameter and logs it itself; to avoid possibly crashing the 
server this way in the future I would have to stop using that gwt-log call 
and intercept all objects logged to gwt-log to make sure the messages in 
the exceptions are not too big.

Original issue reported on code.google.com by [email protected] on 15 Oct 2009 at 2:56