[project @ 2005-05-17 12:00:04 by simonmar]

[project @ 2005-05-17 12:00:04 by simonmar]
Improve source locations on error messages from the downsweep.  We now
keep track of SrcSpans from import declarations, so we can report a
proper source location for unknown imports (this improves on the
previous hacky solution of keeping track of the filename that
contained the original import declaration).

ModSummary now contains (Located Module) for each import instead of Module.