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	 	Two minor wibbles
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1.  Make the generic toT/fromT Ids for "generic derived classes" into
    proper ImplicitIds, with their own GlobalIdDetails. This makes it
    easier to identify them.  (The lack of this showed up as a bug
    when I made an apparently-innocuous other change.)

2.  Distinguish ClassOpIds from RecordSelIds in their GlobalIdDetails.
    They are treated differently here and there, so I made this change
    as part of (1)

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