(which is the case in sdists)

Fulfils Trac #4369

This fixes Trac #4397.  See comments with 'isMoreSpecific'.

  See Note [Touchable meta type variables] in TcSMonad

These functions were added by

   Tue Apr 18 03:36:06 BST 2006  Lemmih <lemmih@gmail.com>
   * Make the initial rdr and type scope available in the ghc-api

The are extremely dubious, because they extend the Rdr and Type
env for every compilation.  The right thing to do is to use
the InteractiveContext for temporary extensions.

So far as we know, no one uses them.  And if they are being used
it's probably a mistake.  So we're backing them out.

This doesn't fix anything (we think), but it's morally correct.

Debugged thanks to lots of help from Simon PJ: we weren't updating the
UnfoldingGuidance when the unfolding changed.
Also, a bit of refactoring and additinoal comments.

Set tso->why_blocked before calling maybePerformBlockedException(), so
that throwToSingleThreaded() doesn't try to unblock the current thread
(it is already unblocked).

This is patch that adds support for interruptible FFI calls in the form
of a new foreign import keyword 'interruptible', which can be used
instead of 'safe' or 'unsafe'.  Interruptible FFI calls act like safe
FFI calls, except that the worker thread they run on may be interrupted.

Internally, it replaces BlockedOnCCall_NoUnblockEx with
BlockedOnCCall_Interruptible, and changes the behavior of the RTS
to not modify the TSO_ flags on the event of an FFI call from
a thread that was interruptible.  It also modifies the bytecode
format for foreign call, adding an extra Word16 to indicate
interruptibility.

The semantics of interruption vary from platform to platform, but the
intent is that any blocking system calls are aborted with an error code.
This is most useful for making function calls to system library
functions that support interrupting.  There is no support for pre-Vista
Windows.

There is a partner testsuite patch which adds several tests for this
functionality.

Stops us accidentally depending on them

We used to define these CPP symbols, but nothing on hackage uses them
and the first 2 are no longer correct (as we support multiple Haskell
versions).

For now we don't build the Cabal userguide, but we should add markdown
support so that we can do so.

The default language is now Haskell2010, so this was a little odd.
Also, --make is now on by default, so this was largely irrelevant.

This means most code doesn't get caught by monomorphic local bindings.

Instead of keeping a *set* of untouchable variables in each
implication contraints, we keep a *range* of uniques for the
*touchable* variables of an implication.  This are precisely
the ones we would call the "existentials" if we were French.

It turns out that the code is more efficient, and vastly easier
to get right, than the set-based approach.

Fixes Trac #4355 among others

This fixes Trac #4361.  In a rather delicate way, but
no more delicate than before.  A more remoseless typechecker
would reject #4361 altogether.

See Note [Avoid unecessary constraint simplification]

Note [Avoid unecessary constraint simplification] in TcSimplify

This fixes at least one case of performance regression in 7.0, and
is nice win on nofib:

        Program           Size    Allocs   Runtime   Elapsed
            Min          +0.3%    -63.0%    -38.5%    -38.7%
            Max          +1.2%     +0.2%     +0.9%     +0.9%
 Geometric Mean          +0.6%     -3.0%     -6.4%     -6.6%

The error cascade caused puzzling errors in T4093b, and
suppressing some seems like a good plan.  Very few test
outputs change.

This big-ish patch arranges that if an Id 'f' is 
  * Type-class overloaded 
       f :: Ord a => [a] -> [a]
  * Defined with an INLINABLE pragma
       {-# INLINABLE f #-}
  * Exported from its defining module 'D'

then in any module 'U' that imports D

1. Any call of 'f' at a fixed type will generate 
   (a) a specialised version of f in U
   (b) a RULE that rewrites unspecialised calls to the
       specialised on

  e.g. if the call is (f Int dOrdInt xs) then the 
  specialiser will generate
     $sfInt :: [Int] -> [Int]
     $sfInt = <code for f, imported from D, specialised>
     {-# RULE forall d.  f Int d = $sfInt #-}

2. In addition, you can give an explicit {-# SPECIALISE -#}
   pragma for the imported Id
     {-# SPECIALISE f :: [Bool] -> [Bool] #-}
   This too generates a local specialised definition, 
   and the corresponding RULE 

The new RULES are exported from module 'U', so that any module
importing U will see the specialised versions of 'f', and will
not re-specialise them.

There's a flag -fwarn-auto-orphan that warns you if the auto-generated
RULES are orphan rules. It's not in -Wall, mainly to avoid lots of
error messages with existing packages.

Main implementation changes

 - A new flag on a CoreRule to say if it was auto-generated.
   This is persisted across interface files, so there's a small
   change in interface file format.

 - Quite a bit of fiddling with plumbing, to get the 
   {-# SPECIALISE #-} pragmas for imported Ids.  In particular, a
   new field tgc_imp_specs in TcGblEnv, to keep the specialise
   pragmas for imported Ids between the typechecker and the desugarer.

 - Some new code (although surprisingly little) in Specialise,
   to deal with calls of imported Ids