work in progress refactoring wait/notify

adds Condition type, for use anywhere you need to wait for something.
removes WaitFor and WorkItem, simplifying RemoteRefs. not tested yet.
the I/O code will be migrated to this next.
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars
use Condition for stream and process
remove the filter argument from wait(). this simplifies things a lot.
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars
Reorganize stream server code
Fix bug in listen/accept
fix some typos
restore the try block for catching EOF and deserialization errors. this
allows workers to exit when the head node quits (usually).
print errors in multi.jl to stderr
fix a couple extra problems, make tests pass
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars
move stat.jl before fs.jl, which now needs it