SI-6745 Fix <init> lookup

We should only consult the decls of the enclosing
class. Members of the self type, enclosing scopes,
or imports should not be considered.
Rewrote FastTrack for clarity.

We can say what we wish to say with more directness
and with fewer vars, levels of indirection, public members,
and implicit conversions.
adds Tree.nonEmpty

So that trees become consistent with isEmpty on lists and options.
Adds extractors for TypeName, TermName and Modifiers

This change allows to pattern match over type names, term names and
modifiers. Otherwise it can be quite painful to match over complex trees
as each name or modifiers requires a guard.

This pull request also changes the name of default constructor for term
and type names i.e. TypeName(s) instead of newTermName(s). This is
shorter to type, more consistent with the rest of reflection api and
consistent with the way it will be pattern matched later on.
Changes reifier to use shorter name constructors
Changes tree pretty printer to use shorter name constructors
Changes reflection tests to use shorter name constructors
renames c.fresh to c.freshName
Removed old pattern matcher.
Merge pull request #1806 from paulp/pr/fasttrack

Rewrote FastTrack for clarity.
Merge pull request #1820 from paulp/pr/what-old-patmat

Removed old pattern matcher.
Merge pull request #1786 from retronym/ticket/6745-3

SI-6745 Fix <init> lookup
Removed dead implementation.

Another "attractive nuisance" burning off time until I
realized it was commented out.
Fix and simplify typedTypeConstructor.

Investigating the useful output of devWarning (-Xdev people,
it's good for you) led back to this comment:

  "normalize to get rid of type aliases"

You may know that this is not all the normalizing does.
Normalizing also turns TypeRefs with unapplied arguments
(type constructors) into PolyTypes. That means that when
typedParentType would call typedTypeConstructor it would
find its parent had morphed into a PolyType. Not that it
noticed; it would blithely continue and unwittingly discard
the type arguments by way of appliedType (which smoothly
logged the incident, thank you appliedType.)

The simplification of typedTypeConstructor:

There was a whole complicated special treatment of AnyRef
here which appears to have become unnecessary. Removed special
treatment and lit a candle for regularity.

Updated lots of tests regarding newly not-so-special AnyRef.
Shored up a hidden dealiasing dependency.

Like the comment says:

// This way typedNew always returns a dealiased type. This
// used to happen by accident for instantiations without type
// arguments due to ad hoc code in typedTypeConstructor, and
// annotations depended on it (to the extent that they worked,
// which they did not when given a parameterized type alias
// which dealiased to an annotation.) typedTypeConstructor
// dealiases nothing now, but it makes sense for a "new" to
// always be given a dealiased type.

PS:
Simply running the test suite is becoming more difficult all
the time. Running "ant test" includes time consuming activities
of niche interest such as all the osgi tests, but test.suite
manages to miss the continuations tests.
Cleaning up type alias usage.

I determined that many if not most of the calls to .normalize
have no intent beyond dealiasing the type. In light of this I
went call site to call site knocking on doors and asking why
exactly they were calling any of

  .normalize
  .widen.normalize
  .normalize.widen

and if I didn't like their answers they found themselves
introduced to 'dropAliasesAndSingleTypes', the recursive widener
and dealiaser which I concluded is necessary after all.

Discovered that the object called 'deAlias' actually depends
upon calling 'normalize', not 'dealias'. Decided this was
sufficient cause to rename it to 'normalizeAliases'.

Created dealiasWiden and dealiasWidenChain.

Dropped dropAliasesAndSingleTypes in favor of methods
on Type alongside dealias and widen (Type#dealiasWiden).
These should reduce the number of "hey, the type alias doesn't work" bugs.
SI-6846, regression in type constructor inference.

In 658ba1b4e6 some inference was gained and some was lost.
In this commit we regain what was lost and gain even more.
Dealiasing and widening should be fully handled now, as
illustrated by the test case.
Merge pull request #1826 from adriaanm/paulp-pr-dealiasWiden

uniform dealiasing and widening
cleans up usages of <init>
Merge pull request #1811 from scalamacros/topic/tree-nonempty

adds Tree.nonEmpty