Allow naming a runAsync call using a class literal.  There are now
two overloads of GWT.runAsync, and the new overload takes an
extra argument supplying the class literal.

Review by: kprobst (SplitPointRecorder), scottb (the bulk of it)


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6097 8db76d5a-ed1c-0410-87a9-c151d255dfc7