global build dependencies.  The correct solution is to add global
dependencies to each executable and implement dependency resolution
for executables.

The current workaround is to add the dependencies to the library, but
disable building of the library.

interface changes.

simple strings.

information of CondTrees is now a modifier.  Move CondTree resolution functionality. 

function to accept an arbitrary partial assignment of these
variables.

Used to be if __GLASGOW_HASKELL__ >= 604, but the 6.4 branch had a bug
which looks likely to be the cause of GHC build failures we're seeing:
-         procNextOpt (NonOpt x)   RequireOrder      = ([],x:rest,us,[])
+         procNextOpt (NonOpt x)   RequireOrder      = ([],x:rest,[],[])

The haddock --css flag is new. The old --hscolour=[path] flag got split
into two flags: --hyperlink-source and --hscolour-css=path