-------------------------------------
	   Complete an earlier TH commit
	-------------------------------------

In this earlier commit:

  3.  Ensure that a declaration quotation [d| ... |] does not have a
      permanent effect on the instance environment. (A TH fix.)

I had forgotten to do a stage2 compile.  This commit just completes
the earlier work.  I moved some code from TcExpr (long) to TcSplice
(shorter) which had the happy effect of bringing related code together.