Patch from Christian Maeder

This comes from the Debian automake 1:1.10+nogfdl-1 package.

If Cabal doesn't see the .ly file then it won't try to run happy, and
thus won't fail if happy isn't installed.

Slackware puts the stylesheets in /usr/share/xml/docbook/xsl-stylesheets*
Patch from Andrea Rossato.

This patch is on the HEAD.  It fixes a nasty and long-standing bug
whereby we weren't substituting the ru_fn field of a CoreRule in 
CoreSubst.substSpec, which ultimately led to a puzzling "nameModule"
error trying to put the rules in the interface file.

The problem was that because the interface hadn't changed, we were
re-using the old ModIface.  Unfortunately the ModIface contains the
GlobalRdrEnv for the module, and that *had* changed.  The fix is to
put the new GlobalRdrEnv in the ModIface even if the interface has not
otherwise changed.

ModIface is not really the right place for the GlobalRdrEnv, but
neither is ModDetails, so we should think about a better way to do
this.

Sorry, should have pushed with previous batch of changes.

Tabs aren't guaranteed to be 8 spaces on every output device, so we
shouldn't be using them.  Instead I added a little optimisation to
use chunks of 8 spaces for long indentations.

- :def! now overwrites a previous command with the same name
- :def on its own lists the defined macros
- ":undef f g" undefines both f and g

   
  - :browse!
    a variant of :browse that lists children separately,
    not in context, and gives import qualifiers in comments

SimonM: I also added sorting by source location for interpreted
modules in :browse, and alphabetic sorting by name otherwise.  For
:browse *M, the locally-defined names come before the external ones.

  - :{ ..lines.. :} (multiline commands)
    allow existing commands to be spread over multiple lines
    to improve readability, both interactively and in .ghci
    (includes a refactoring that unifies the previous three
    command loops into one, runCommands, fed from cmdqueue,
    file, or readline)

  - :set
      now shows GHCi-specific flag settings (printing/
      debugger), as well as non-language dynamic flag 
      settings
    :show languages
      show active language flags
    :show packages
      show active package flags as well as implicitly 
      loaded packages

See Note [Silly type synonym] in TcType for further details.  This bug
(or at least infelicity) has been in GHC for quite a long time.

An Id bound by GHCi from a previous Stmt is Global but Internal, and
I'd forgotten that, leading to unnecessary restrictions when using TH
and GHCi together.

This patch fixes the problem and adds lots of explanatory comments (which
is where most of the extra lines come from).

Merge to 6.8 branch

Does what the name suggests: it performs the function of both
checkModule and load on that module, avoiding the need to process each
module twice when checking a batch of modules.  This will make Haddock
and ghctags much faster.

Along with this is the beginnings of a refactoring of the HscMain
interface.  HscMain now exports functions for separately running the
parser, typechecher, and generating ModIface and ModDetails.
Eventually the plan is to complete this interface and use it to
replace the existing one.

 - take the GHC topdir as a runtime argument
 - deal with files one at a time (fix space leak)