Make the version number match the cabal file's version number.

This is necessary because otherwise the linker flags given at pkgs/build-support/cabal/default.nix:201-203 are ineffective, which causes the built binary to be unable to find its .so file at runtime.  This appears to only affect executables that are built in the same cabal package as the library they require.
Upgrade ghcjs to a newer checkout.  Not working yet, but making it to ghcjs-boot.