Fix some missed opportunities for preInlineUnconditionallywip/T18815

There are two signficant changes here:

* Ticket #18815 showed that we were missing some opportunities for
  preInlineUnconditionally.  The one-line fix is in the code for
  GHC.Core.Opt.Simplify.Utils.preInlineUnconditionally, which now
  switches off only for INLINE pragmas.  I expanded
  Note [Stable unfoldings and preInlineUnconditionally] to explain.

* When doing this I discovered a way in which preInlineUnconditionally
  was occasionally /too/ eager.  It's all explained in
  Note [Occurrences in stable unfoldings] in GHC.Core.Opt.OccurAnal,
  and the one-line change adding markAllMany to occAnalUnfolding.

I also got confused about what NoUserInline meant, so I've renamed
it to NoUserInlinePrag, and changed its pretty-printing slightly.
That led to soem error messate wibbling, and touches quite a few
files, but there is no change in functionality.

I did a nofib run.  As expected, no significant changes.

        Program           Size    Allocs
----------------------------------------
         sphere          -0.0%     -0.4%
----------------------------------------
            Min          -0.0%     -0.4%
            Max          -0.0%     +0.0%
 Geometric Mean          -0.0%     -0.0%

I'm allowing a max-residency increase for T10370, which seems
very irreproducible. (See comments on !4241.)  There is always
sampling error for max-residency measurements; and in any case
the change shows up on some platforms but not others.

Metric Increase:
    T10370

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/GHC/Parser.y b/compiler/GHC/Parser.y
index b8a777a8fe..b688b86310 100644
--- a/compiler/GHC/Parser.y
+++ b/compiler/GHC/Parser.y
@@ -2513,7 +2513,7 @@ sigdecl :: { LHsDecl GhcPs }
         | '{-# SPECIALISE' activation qvar '::' sigtypes1 '#-}'
              {% ams (
                  let inl_prag = mkInlinePragma (getSPEC_PRAGs $1)
-                                             (NoUserInline, FunLike) (snd $2)
+                                             (NoUserInlinePrag, FunLike) (snd $2)
                   in sLL $1 $> $ SigD noExtField (SpecSig noExtField $3 (fromOL $5) inl_prag))
                     (mo $1:mu AnnDcolon $4:mc $6:(fst $2)) }