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	Expression simplification for TH
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Simplify expressions without any inlining in SimplCore.simplifyExpr.

simplifyExpr is used to simplify a TH splice before running the code,
and simplifyExpr was using (SimplPhase 0) which allows inlining.
Unfortunately, when -O is on (which can happen when compiling a program
with some splices with -O) some inlining can happen which then confuses
the byte-code generator.  (Unboxed tuples.)