This uses `cabal configure` to determine which exact dependency versions
we are compiling against, and ensures that these versions are used
by passing -package-id flags to GHC.

The `cabal configure` step makes the build fail before compiling / type
checking if the user tries to compile against a dependency version we don't
support; before, this case led to type errors which were not clearly
user errors. This fixes issue #988.

The output of `cabal configure` is also used to generate MIN_VERSION_*
macros.

MIN_VERSION_* macros are the standard way to build CPP dependency switches
in Haskell packages, and they replace our custom macros (like PARALLEL3
and NO_REGEX_PCRE) which had to be hand-built for each dependency.
We can now query the version of any Haskell dependency without having
to manually add a flag via autoconf.

All ghc and hlint invocations were adjusted to take these macros into
account.

This change introduces a Haskell-build-time dependency on cabal-i...