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.
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
Merge branch '2.10.x' into topic/merge-v2.10.2-RC1-35-ga54d86b-to-master

Conflicts:
	src/partest/scala/tools/partest/DirectTest.scala
Merge pull request #2647 from retronym/topic/merge-v2.10.2-RC1-35-ga54d86b-to-master

merge 2.10.x to master