Summary:
This adds generic support for reporting error traces as usual infer issues
traces (instead of putting them in the textual description of the error) to
Trace.ml and SinkTrace.ml.
The siof checker is made to use these new traces, and gets an improved error
message mentioning the name of the problematic global as well, which requires a
slight API change in Pvar.re.
The support in Trace.ml is incomplete: passthroughs are ignored. This missing
feature will be needed by Quandary to migrate its error messages.
Reviewed By: sblackshear
Differential Revision: D4159542
fbshipit-source-id: 8c1101d