Update transformers submodule to new v0.4 rel

This also updates the haskeline to upstream master to
accomodate the new transformers version
Improve tracing in Simplifier
Refactor buildClass and mkDictSelId a bit, to avoid the no_unf argument

No change in functionality, just a cleaner story, with the RHS for
dictionary selectors being treated less specially than before.
Mark evaluated arguments in dataConInstPat

See Note [Mark evaluated arguments] in CoreUtils.

This is not a significant change, but avoids a spurious Lint complaint.
Preserve evaluated-ness in CoreTidy

The main effect of this patch is to preserve the evaluated-ness of
case binders and suchlike, to avoid spurious Lint complaints after
tidying.  See Note [Preserve evaluatedness] in CoreTidy.

Plus a bit of associated refactoring of tidyIdBndr, tidyLetBndr.
Better error message in vectoriser
Error message wibble, presumably due to recent changes in transformers
Update .gitignore

Signed-off-by: Austin Seipp <austin@well-typed.com>
testsuite: fix cgrun051 exit code

Signed-off-by: Austin Seipp <austin@well-typed.com>
testsuite: fix cc004

Signed-off-by: Austin Seipp <austin@well-typed.com>
Require transformers for T5979

in order to get a reliable error message
(although the error message could be improved anyways to mention the
explicit package the module is imported with.)
Revert output of T5979

this reverts 12332f1. The error message changes when there are two
versions of transformers in the database, one of them hidden. That might
be a bug of its own, but for now lets make the test case succeed after a
fresh build. Affected developers should probably
$ ./inplace/bin/ghc-pkg unregister transformers-0.3.0.0
Comments only, on inert_fsks and inert_no_eqs

I wrote these when studying Trac #9090
In splitHsFunType, take account of prefix (->)

This fixes Trac #9096
Improve desugaring of lazy pattern match

This patch implements a simpler, and nicer, desugaring for
lazy pattern matching, fixing Trac #9098
Typo in comment
Typo in note
Lint should check that TyConAppCo doesn't have a synonym in the tycon position

That is why Lint didn't nail Trac #9102
Fix invariant in mkAppCoFlexible

mkAppCoFlexible was breaking the invariant that the head of a TyConAppCo cannot
be a type synonym.  This small patch fixes it.
Fix globalRegMaybe for unregisterised build.

In commit 83a003f globalRegMaybe will be called but panics
for unregisterised compilers.

In an unregisterised compiler there are no global registers
so always return `Nothing`.

Fixes #9055.