TH:
- We are forcing importing THSyntax.Q at every top splice now; this suffices
  to get simple splices that do not involve reifyDecl or declaration
  quasi-quotes to work.  NB: This worked already when the construction of the
  Dec term and the splice were in separated modules, but not when they are in
  the same (see the regression test "TH_spliceDecl1.hs").
- The tests "TH_spliceDecl2.hs" and "TH_spliceDecl3.hs" use toplevel splices
  together with quasi-quoted and reifyDecl.  These currently still fail, as
  importing of some of the required type constructors from THSyntax isn't
  forced.