We actually need to use -threaded/-debug when linking /all/ DLLs

Not just base, integer-gmp and ghc-prim.
More work towards dynamic programs on Windows

Dynamic GHC is now working in-place, but pathologically slow due
to the DLL split.

(GHC assumes that all intra-package calls are in the same DLL, but that
isn't true when we split the GHC package into 2 DLLs. That means that
GHC's startup time is around 22 seconds, as it is doing run-time
linking).

Also, ghci isn't actually working yet:

$ inplace/bin/ghc-stage2 --interactive
GHCi, version 7.7.20130512: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... <command line>: can't load .so/.DLL for:
HSghc-prim-0.3.1.0.dll (addDLL: could not load DLL)
ghc-stage2.exe: HSghc-prim-0.3.1.0: The specified module could not be
found.
Merge win:/cygdrive/c/ghc/git/dt
Merge branch 'master' of http://darcs.haskell.org/ghc