[GHC] #14023: Split up glasgow_exts.rst

[GHC]

#14023: Split up glasgow_exts.rst
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Documentation     |              Version:  8.0.1
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by AntC):

 I support splitting up the file: It is nerve-wracking to edit it for fear
 of mucking up a section you never intended to touch. Previewing it to see
 your edits takes a long wait for rendering. And it's too easy to mess up
 the formatting with result that the contents/index turns to custard.

 OTOH there are many cross-references amongst different subsections. Is
 `.rst` clever enought to stitch togethere the labels?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14023#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler