Fix build on Win64

gcc thought that fourthFloating could be used without being defined.
In actual fact it couldn't, but I've refactored the code so that it
can now see this.
Fix bumpTickyLitBy[E] on Win64; fixes #7940

A comment claimed that the ticky counters are unsigned longs, but
as far as I can see that isn't the case: They're already word-sized
values.
Track haskeline Win64 fix
Change the ranlib detection

On Windows, the ranlib in the path may not be the right ranlib (it may
be the 32bit ranlib when we are making a Win64 compiler, or vice-versa).
Therefore we can't leave it up to libffi to detect the right ranlib, but
need to tell it which ranlib to use. This means that we need to find
ranlib even if we don't actually need it ourselves.
Merge branch 'master' of http://darcs.haskell.org/ghc