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These indicate the size and time span of a sequence of events in the
event log, to make it easier to sort and navigate a large event log.

Flags (from +RTS -?):

  -qg[<n>]  Use parallel GC only for generations >= <n>
            (default: 0, -qg alone turns off parallel GC)
  -qb[<n>]  Use load-balancing in the parallel GC only for generations >= <n>
            (default: 1, -qb alone turns off load-balancing)

these are good defaults for most parallel programs.  Single-threaded
programs that want to make use of parallel GC will probably want +RTS
-qg1 (this is documented).

I've also updated the docs.

In particular, remove the claim that the GC is single-threaded!

Using "builtin:foo" creates a file called "builtin" on Windows

It confuses the build system.

They no longer exist.

It was using the old filename, rather than the new directory name.

Performance isn't an issue for reading the old-style package.conf
files, so we might as well revert to using read and fix a bug at the
same time.

This patch fixes test failures for the profiling way for drv001.
The problem was that the arity of a function was decreasing during
"optimisation" because of interaction with SCC annotations.
In particular
      f = /\a. scc "f" (h x)    -- where h had arity 2
and h gets inlined, led to
      f = /\a. scc "f" let v = scc "f" x in \y. <blah>

Two main changes:

1.  exprIsTrivial now says True for (scc "f" x)
    See Note [SCCs are trivial] in CoreUtils

2.  The simplifier eliminates nested pushing of the same cost centre:
  	scc "f" (...(scc "f" e)...) 
  	==>  scc "f" (...e...)

This patch implements three significant improvements to Template Haskell.
  
Declaration-level splices with no "$" 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This change simply allows you to omit the "$(...)" wrapper for 
declaration-level TH splices.  An expression all by itself is
not legal, so we now treat it as a TH splice.  Thus you can now
say
	data T = T1 | T2
 	deriveMyStuff ''T

where deriveMyStuff :: Name -> Q [Dec]
This makes a much nicer interface for clients of libraries that use
TH: no scary $(deriveMyStuff ''T).

Nested top-level splices
~~~~~~~~~~~~~~~~~~~~~~~~
Previously TH would reject this, saying that splices cannot be nested:
	f x = $(g $(h 'x))
But there is no reason for this not to work.  First $(h 'x) is run,
yielding code <blah> that is spliced instead of the $(h 'x). Then (g
<blah>) is typechecked and run, yielding code that replaces the
$(g ...) splice.  

So this simply lifts the restriction.

Fix Trac #3467: non-top-level type splices
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It appears that when I added the ability to splice types in TH
programs, I failed to pay attention to non-top-level splices -- that
is, splices inside quotatation brackets.  

This patch fixes the problem.  I had to modify HsType, so there's a
knock-on change to Haddock.

Its seems that a lot of lines of code has changed, but almost all the
new lines are comments!

General tidying up
~~~~~~~~~~~~~~~~~~
As a result of thinking all this out I re-jigged the data type ThStage,
which had far too many values before.  And I wrote a nice state transition
diagram to make it all precise; 
   see Note [Template Haskell state diagram] in TcSplice

Lots more refactoring in TcSplice, resulting in significantly less code.
(A few more lines, but actually less code -- the rest is comments.)

I think the result is significantly cleaner.