In particular, we now ignore .git directories

Given the high impact of this change, we decided to back off and make
abstract newtypes give a warning for one release, before we make it an
error in 7.6.1.

Codec/Compression/Zlib/Stream.hsc:884:1:
    Warning: newtype `CInt' is used in an FFI declaration,
             but its constructor is not in scope.
             This will become an error in GHC 7.6.1.
    When checking declaration:
      foreign import ccall unsafe "static zlib.h deflate" c_deflate
        :: StreamState -> CInt -> IO CInt

This featurelet allows Trac #5237 to be fixed.
The idea is to allow SPECIALISE pragmas to specify
the phases in which the RULE is active, just as you can
do with RULES themselves.
  {-# SPECIALISE [1] foo :: Int -> Int #-}

This feature is so obvious that not having it is really a bug.
There are, needless to say, a few wrinkles.  See
   Note [Activation pragmas for SPECIALISE]
in DsBinds

Conflicts:
	compiler/ghci/ByteCodeItbls.lhs

Was causing occasional failure in some threaded2 tests.

If a file we depended on last time is missing, we should recompile.

This also makes us insensitive to mistakes when recording dependent
source files (such as storing a temporary file), but will make more
recompilation happen instead.  With DEBUG on, you get a warning.

This bug caused Trac #5655

This improves compile times slightly.

Fixes ticket #5472

Better to specifically list the unsupported cases in code
than to have a catch all that panics. The later method hides
problems when new constructors are added such as the recent
additions to the supported Cmm prim ops that weren't ported
to the C backend since no one noticed.

hppa1, m68k