[GHC] #15018: Bump base's version number to 4.12.0.0 in HEAD

[GHC]

#15018: Bump base's version number to 4.12.0.0 in HEAD
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           Reporter:  RyanGlScott    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  libraries      |           Version:  8.5
  (other)                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Currently, `base` sits at version `4.11.0.0` in HEAD (which is the same
 version of `base` as shipped with GHC 8.4.1). This is making it difficult
 to adapt certain Hackage libraries to recent changes in `base`, such as
 moving `Data.Functor.Contravariant` into `base` (see the discussion
 [https://github.com/ekmett/contravariant/issues/44 here]).

 Before we can do this, here is a list of libraries that will need to have
 their upper version bounds on `base` bumped from `< 4.12` to `< 4.13`:

 * `array`
 * `deepseq`
 * `directory`
 * `filepath`
 * `ghc-boot-th`
 * `ghc-compat`
 * `ghci`
 * `haddock`
 * `haskeline`
 * `hpc`
 * `parallel`
 * `parsec`
 * `primitive`
 * `process`
 * `stm`
 * `template-haskell`
 * `terminfo`

 Some of these can be changed in-place, while others will require
 downstream changes. I'll update this ticket as I progress.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15018>
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