Implement a job queueing system for running the previewer task worker thread.  My recent runloop changes with other fixes in the TeX task apparently threw off the timing of the previous code, which seemed to rely on oneway message queuing.
Implement a job queueing system for running the previewer task worker thread.  My recent runloop changes with other fixes in the TeX task apparently threw off the timing of the previous code, which seemed to rely on oneway message queuing.

It appears that messages were being dropped, and with the additional asynchronous callback to the previewer, errors (red text with empty log files) were being reported and then soon followed by a successful preview with no interaction.

git-svn-id: cb3fc60f0f557b927b8032d8a94e869b6f9f230b@661 0fceea05-a30d-0410-8a8b-80ef821fb0a1

camillobruni/skim,jasongrout/skim,camillobruni/skim,camillobruni/skim,camillobruni/skim,jasongrout/skim