Remove redundant contexts from Foldable methods

New `Foldable` methods accidentally had `Foldable` contexts, which led
to type roles being assigned incorrectly and preventing GND from
deriving `Foldable` instances. Removing those fixes #9761.

Moreover, this patch takes advantage of this fix by deriving
`Foldable` (and `Eq`) for `UniqFM`.

Differential Revision: https://phabricator.haskell.org/D425
Clean-up Haddock in `Data.Functor`

This mostly cleans up irregularities introduced in
68255588f89462e542c502f6f92548712808032f (re D352) as well as making
sure Haddock is able to resolve all references.
Add `isSubsequenceOf` to Data.List (#9767)

Niklas Hambüchen suggested that we add the dual of `subsequences`,
isSubsequenceOf (like `isPrefixOf` to `inits` & `isSuffixOf` to `tails`).
It was a simple and noncontroversial proposal which passed unanimously.

For more details see the original proposal discussion at
https://www.haskell.org/pipermail/libraries/2014-November/024063.html

Differential Revision: https://phabricator.haskell.org/D435

Signed-off-by: Alexander Berntsen <alexander@plaimi.net>
Fix typo in testsuite Makefile

This is introduced in aa4799534225e3fc6bbde0d5e5eeab8868cc3111
and would cause indeterministic testsuite failures in `sigof02dmt`
Fix a couple of bugs in the way info tables are generated for 64-bit platforms

1. The offset was a full word, but it should actually be a 32-bit
offset on 64-bit platforms.
2. The con_desc string was allocated separately, which meant that it
might be out of range for a 32-bit offset.

These bugs meant that +RTS -Di (interpreter debugging) would sometimes
crash on 64-bit.
Fix bugs in debug printing
Fix a couple of inaccurate stack checks
Disable an assertion; see comment
Add a comment about stack checks
Add doctest examples for Data.Either

Add doctest examples for every data type and function in `Data.Either`

Differential Revision: https://phabricator.haskell.org/D443
Clarify confusing notice from `make maintainer-clean`
Remove -ddump-simpl-phases flag
Remove -ddump-core-pipeline flag
Update User's Guide, cleanup DynFlags