This also removes the dependency on alex and happy.
This should work on Windows, unlike the TH solution with file-embed.
It is needed for the Windows installer, since if a library is produced, the binary can't be made relocatable. See http://www.haskell.org/ghc/docs/6.12.2/html/Cabal/builders.html section 188.8.131.52.
Reason: starting with Cabal 1.8, installing pandoc with '-library +executable' did not work, since the build-depends in the Library stanza were ignored. The problem could be solved by repeating the build-depends in the Executable stanza, but this seems non-ideal (and might lead to errors later on). The '-library' option isn't so useful anyway, since to compile pandoc in the first place, you need a large number of Haskell libraries installed, and in this case, why balk at another? It was chiefly intended for packagers, but packagers will need to use a chroot environment anyway, and they can then simply copy the executable and not the library. Thanks to Jim Pryor for calling the problem to my attention in connection with an arch linux package.