Temporary reversion of a bit of d8b96bb858.

If I reverse these few lines, I can rebase miguel's
pull request cleanly; if I don't, git thinks there are
enough merge conflicts to start a war. Something is
suboptimal in that algorithm.
warn about uninitialized reads (in constructors), self-contained check

The check in question relies on helper maps and methods that don't
belong outside that check. This commit encapsulates those helpers into
the newly added `checkUninitializedReads()` , thus uncluttering
`transformClassTemplate()`
handling AnyVal special case early on to simplify logic afterwards

This way the contract of `transformClassTemplate()` can focus on
non-AnyVal cases, which are more regular from the perspective of
transforming their templates in the constructors phase.
how stuff works: elision of param-accessor-fields and outer-accessors
eliding what the constructor phase elides but with less effort (1 of 2)

For now both old and new implementations of elision coexist,
allowing cross-checking their results.
In the next commit only the new one will remain.
eliding what the constructor phase elides but with less effort (2 of 2)

Removing the old implementation of elision in constructors
in favor of the new one which is both faster, more readable.
method transformClassTemplate() turned into class TemplateTransformer
separation of concerns: delayed-init in constructors
separation of concerns: elision in constructors
readability for intoConstructors transformer
separation of concerns: guard non-specialized ctor-stats in constructors
skipping trips to specializeTypes when not necessary in constructors
Reversing reversion of ac6504b8c4.

Putting back the bits I moved aside to get a clean rebase.
Golfed about 20 lines into the sand trap.

And it's a nice golf clinic and all, but let's remove our
golf gloves and take in some film.

  for (stat <- defBuf.iterator ++ auxConstructorBuf.iterator)

A quick count:

 - defBuf is a ListBuffer (1 mutant)
 - auxConstructorBuf is a ListBuffer (2 mutants)
 - two mutable iterators over mutable sequences (3, 4 mutants)
 - Iterator.++ joins them and is BY-NAME (4 mutants, 1 tragedy in waiting)
 - the joined Iterator is a new mutable structure (5 mutants, now 3 deep)
 - omittables is a mutable Set (6 mutants)
 - the 5-layer-3-deep iterator mutates omittables as it walks

[The following is a public service breakdown. The letter
sequence y-o-u is a local variable which should be replaced
with your name, whoever "you" are, if you commit any code in
these parts.]

Hear my plea! YOU DON'T HAVE TO DO IT THIS WAY! It isn't simpler,
faster, easier, more satisfying, shorter, more pixelated, there
just isn't any advantage to it, even if you're lazy! Especially
if you're lazy! Whatever combination of virtues and vices exist
in your personal petri dish, this will never be a hilltop!

PLEASE COME ENJOY A DRINK WITH ME AND MY FRIEND 'VAL' !!
I'LL INTRODUCE YOU! I THINK YOU WILL REALLY LIKE HER! I HOPE
YOU WILL SEE A LOT OF ONE ANOTHER! REMEMBER THAT NAME, 'VAL' !!
SHE'LL HAVE HER EYE OUT FOR YOU!
new starr that supports macro ???
less magic in fast track macros

Now that we have a mechanism to declare not implemented macros, let's put
it to good use by reducing the amount of magic applied to fast track.
SI-7461 c.typeCheck(silent = true) now suppresses ambiguous errors

Otherwise use cases like the one shown in the attached test (trying to
typecheck something, which leads to an ambiguous overload error) will
mysteriously fail compilation.
macro engine refactoring

Macro impl bindings now store more information in signatures.
Previously it was a flattened List[Int] corresponding to flattened paramss,
now it's List[List[Int]] to preserve the lengths of parameter lists.
Also now we distinguish between c.Expr parameters and others.

Previously actual and reference macro signatures were represented as
tuples of vparamss, rets, and sometimes tparams. Now they are all
abstracted behind MacroImplSig.

Finally this patch provides better error messages in cases of
argsc <-> paramsc and argc <-> paramc mismatches.
refactors macro tests

putting in a nutshell, this patch:
  * condenses some macro-XXX-a/b/c/... bundles
  * renames some tests to prepare for other macro flavors
  * introduces some additional tests
refactors importers

Introduces better names, factors out recreation of symbols, trees, types
and completes into separate methods, so that they can be overridden in
specialized importers.

The original motivation for this refactoring was to support JIT
compilation of macros, but I think that most of the introduced
improvements to code quality will be useful in trunk.