Make GHCi & TH work when the compiler is built with -prof

Summary:
Amazingly, there were zero changes to the byte code generator and very
few changes to the interpreter - mainly because we've used good
abstractions that hide the differences between profiling and
non-profiling.  So that bit was pleasantly straightforward, but there
were a pile of other wibbles to get the whole test suite through.

Note that a compiler built with -prof is now like one built with
-dynamic, in that to use TH you have to build the code the same way.
For dynamic, we automatically enable -dynamic-too when TH is required,
but we don't have anything equivalent for profiling, so you have to
explicitly use -prof when building code that uses TH with a profiled
compiler.  For this reason Cabal won't work with TH.  We don't expect
to ship a profiled compiler, so I think that's OK.

Test Plan: validate with GhcProfiled=YES in validate.mk

Reviewers: goldfire, bgamari, rwbarton, austin, hvr, erikd, ezyang

Reviewed By: ezyang

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1407

GHC Trac Issues: #4837, #545