SI-6138 Centralize and refine detection of `getClass` calls

`getClass` is special cased in the compiler; this is described
in in the comments on `Definitions.Any_getClass`.

Part of this happens in `Typer#stabilize`. This was trying to determine
if an Ident or Select node was a call to `getClass` by merits of the name
of the tree's symbol and by checking that the its type (if it was a
MethodType or PolyType) had no parameters in the primary parameter list.

Overloaded user defined `getClass` methods confused this check. In the
enclosed test case, the tree `definitions.this.getClass` had an
`OverloadedType`, and such types always report an empty list of `params`.

This commit:

  - changes `stabilize` to use `isGetClass`, rather than the
    homebrew check
  - changes `isGetClass` to consider a `Set[Symbol]` containing all
    `getClass` variants. This moves some similar code from `Erasure`
    to `Definitions`
  - keeps a fast negative path in `isGetClass` based on the symbol's name
Merge pull request #2578 from retronym/ticket/6138

SI-6138 Centralize and refine detection of `getClass` calls
Test for reading JDK 8 (classfile format 52) class files.

This commit includes a test for reading JDK 8 (classfile format 52)
class files, in particular default (aka defender) methods. It uses ASM
to generate an interface with default methods then exercises that
interface from Scala.

Surprisingly no changes are necessary to the Scala code base to support
reading format 52 class files.

Because the test can only run under JDK 8, the JDK version is checked
and the expected output is synthesized for previous versions.
SI-6841 Fix bug at the intersection of DelayedInit and named args

The DelayedInit transformation analyses the constructor to partition
regular initialization from calls to super constructors / trait
initializers.

It failed to find such super calls if they were nested in a Block,
which can happens when using named or default arguments.

This commit makes that code peer into Blocks to correctly partition
the constructor statements.

This change doesn't affect the result of run/t4680.scala, which was
mentioned in nearby comments and which chronicles bugs with DelayedInit
when used in inheritance hierarchies.
SI-7507 Fix lookup of private[this] member in presence of self type.

In the following code:

	trait Cake extends Slice

	trait Slice { self: Cake =>    // must have self type that extends `Slice`
	  private[this] val bippy = () // must be private[this]
	  locally(bippy)
	}

`ThisType(<Slice>)`.findMember(bippy)` excluded the private local member on
the grounds that the first class in the base type sequence, `Cake`, was
not contained in `Slice`.

	scala> val thisType = typeOf[Slice].typeSymbol.thisType
	thisType: $r.intp.global.Type = Slice.this.type

	scala> thisType.baseClasses
	res6: List[$r.intp.global.Symbol] = List(trait Cake, trait Slice, class Object, class Any)

This commit changes `findMember` to use the symbol of the `ThisType`, rather
than the first base class, as the location of the selection.
SI-7375 ClassTag for value class aliases

reifyRuntimeClass now always dealiases its argument prior to processing.
Merge pull request #2619 from scalamacros/ticket/7375

SI-7375 ClassTag for value class aliases
Merge pull request #2609 from retronym/ticket/7507

SI-7507 Fix lookup of private[this] member in presence of self type.
Refactor testing logic for only running under certain JDK versions

We had several tests designed to only run if the JDK version was at
least some specified version. This commit refactors that common logic
into DirectTest.
SI-7556 Fix runtime reflection involving ScalaLongSignature

Scala type information is stored in classfiles in encoded in a String
in the ScalaSignature annotation. When it is too big for a single
String, it is split into an array of Strings in a different annotation,
ScalaLongSignature.

The enclosed test, with a class containing 3000 methods, uses the latter.
It exposes a bug in the way runtime reflection decodes that data.

It must concatentate and *then* decode, rather that the other way around.
SI-7558 Fix capture of free local vars in toolbox compiler

It was creating an `ObjectRef[<notype>]` because of a small
bug in `capturedVariableType`.
Merge pull request #2626 from retronym/ticket/7556

SI-7556 Fix runtime reflection involving ScalaLongSignature
Merge pull request #2629 from retronym/ticket/7558

SI-7558 Fix capture of free local vars in toolbox compiler
Merge pull request #2611 from retronym/ticket/6481

SI-6841 Fix bug at the intersection of DelayedInit and named args
SI-7505 Test case for pattern matcher + type alias bug

Progressed along with SI-7214 in acd74cae09.
Merge pull request #2606 from JamesIry/2.10.x_classfile_52

Test for reading JDK 8 (classfile format 52) class files.
Merge pull request #2616 from retronym/ticket/7505

SI-7505 Test case for pattern matcher + type alias bug
[backport] SI-7498 ParTrieMap.foreach no longer crashes

Previously, the `split` method of the `ParTrieMap` iterator threw
an exception when splitting a splitter that iterated over nodes
whose hash codes collide.
This was due to reusing the iterator of the list of colliding keys
rather than creating a new splitter.

This commit changes the `subdivide` method to create a new
iterator using the factory method of the current trie map
iterator rather than returning a `LinearSeqLike` iterator.
Merge pull request #2644 from retronym/ticket/7498-backport

[backport] SI-7498 ParTrieMap.foreach no longer crashes
[backport] relax time constraint in duration-tck.scala (for Windows VMs)
(cherry picked from commit 3e0fbc0193f0b6f58dc16dae3824677e9902dc7b)