Make Transcript thread-safe #131
Description
Writing from a background process to the transcript still can lead to many race conditions, such as an AssertionFailure during PluggableTextMorphPlus(Morph)>>fullBounds, sent from PluggableTextMorphPlus(PluggableTextMorph)>>handleEdit: and PluggableTextMorphPlus(PluggableTextMorph)>>scrollSelectionIntoView, even when "Force transcript updates to screen" is disabled.
How can we fix that? This seems to require a larger lock ...
But it is hard to reproduce the issue.