[GHC] #9358: Improve flag description in the user guide

[GHC]

#9358: Improve flag description in the user guide
-------------------------------------+-------------------------------------
       Reporter:  jstolarek          |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  low                |               Milestone:  7.10.1
      Component:  Documentation      |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Easy (less than 1  |         Type of failure:
  hour)                              |  Documentation bug
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 Sections 4.20 (Flag reference) and 4.10.2 (-f*: platform-independent
 flags) of the User Guide could use some updating:

   - `-floopification` is mentioned in 4.20 but not in 4.10.2 (which,
 sadly, is my fault),
   - Section 4.10.2 says: "These flags turn on and off individual
 optimisations. They are normally set via the -O options (...) The flags
 below are off by default, except where noted below." Does the last
 sentence mean they are on by default for `-O` or that they are enabled
 even with `-O0` (which is the default optimisation level)?
   - What is the default value of `-fmax-simplifier-iterations`?
   - 4.20 mentions `-fmax-simplifier-iterations`, `-fmax-relevant-bindings`
 and `-fmax-worker-args` but only the first one is described in 4.10.2

 I suspect there are more inconsistencies.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9358>
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