Add basic profiling support to cabal file

Unfortunately, cabal-1.16 has a nasty bug where it ignores
ghc-prof-options on executables[0] even when executable-profiling is
enabled. Hence, to actually make use of this, you have to use
cabal-1.18. Apart from this, however, cabal-1.10 is more than enough,
so we don't actually depend on a later version.

[0] - https://github.com/haskell/cabal/issues/1199