ghci compile option

[goronsf]

Sometimes you want to develop something using ghci, but
a lot of files are just interpreted everytime (which
takes a lot time), while they could also had been
compiled. (An option is writing a simple script each
time (but that's not what users want.) So what I want
(and some people on #haskell): an interface to compile
everything instead of interpretate it.  

So inside ghci I want to have an option: 
:compile which compiles everything (except maybe for
the module you are currently working on.) 

This is how people in #haskell would appreciate it:

21:13 < goron> Is there some command to say in ghci:
precompile everything?
21:13 < goron> I had to write some scripts to do it.
21:14 < Lemmih> goron: ghc --make, perhaps.
21:15 < goron> Lemmih: I meant inside ghci. My approach
was ghc --make, but I had to include a lot of
               paths.
21:15 < goron> And it seems something useful.
21:17 < Lemmih> Agreed.
21:18 < Lemmih> But unfortunately I haven't heard of
such feature.
21:18 < Somebody else> Yep, would be immensly useful.

[simonmar]

I'll take this one. I'm removing the duplication between GhcMode? and HscTarget?, and one nice side-effect should be that it will be possible to compile to object code from inside GHCi.

[simonmar]

See also #934

[simonmar]

Now done, patch is:

Wed Apr 11 03:18:02 PDT 2007  Simon Marlow <simonmar@microsoft.com>
  * Rationalise GhcMode, HscTarget and GhcLink

To compile to object code inside GHCi, use either ghci -fobject-code or :set -fobject-code.