Fix typo in documentation.
SI-7848 Xlint says what looks interpolated

The motivating use case was an Expecty debug string
getting flagged for `$eq`.

The test case demonstrates a different bug, in which
the position of the literal tree is changed when typer
gets rid of the unused local, so that when the tree is
re-typed in erasure, a second, spurious warning is
emitted at the start of the method. Specifically, the
second warning is not suppressed because of the
different position.
add syntactic extractor for assignment-like trees

There are three kinds of assign-like trees:

1. Assign(lhs, rhs)                          // $lhs = $rhs
3. AssignOrNamedArg(lhs, rhs)                // $lhs = $rhs
2. Apply(Select(f, nme.update), args :+ rhs) // $f(..$args) = $rhs

New syntactic combinator unifies all of them and lets users not to think
about these implementations details.
SI-7855 No missing interpolator warning post-typer

Avoid extra work, extra warnings.
SI-7848 Xlint no warn on $sym with params

This idea brought to you by retronym.
Upgrade: starr=M5, partest=RC5, xml=RC4, parsers=RC2.
Follow good interrupt discipline in Response

Restores the interrupted status of the waiting thread after catching
an InterruptException.
SI-7725 - Vector concatenation is unreasonably slow

Rewrote ++ to use append or prepend when adding small collections to the end
or beginning of vectors.  This solves the extra-O(n) problem for addition of
single elements reported in SI_7725.

Renamed LgConcatFaster to Log2ConcatFaster (more widely recognizable).
Merge pull request #2954 from retronym/ticket/7852

Avoid null checks when emitting "".== and SomeModule.==
Merge pull request #2974 from retronym/ticket/7864

SI-7864 Harden "looks like an interpolated String" warning
Merge pull request #2968 from huitseeker/interrupt-kosherness

Follow good interrupt discipline in Response
Merge pull request #2962 from densh/topic/syntactic-assign

Quasiquotes: add syntactic extractor for assignment-like trees
Merge pull request #2953 from jiaweihli/master

Fix typo in documentation.
Merge pull request #2956 from som-snytt/issue/7848-forgotten-interp-msg

SI-7848 Xlint says what looks interpolated
Merge pull request #2972 from adriaanm/versions-m5

Upgrade: starr=M5, partest=RC5, xml=RC4, parsers=RC2.
Merge pull request #2938 from Ichoran/issue/7725

SI-7725 - Vector concatenation is unreasonably slow
Merge pull request #2975 from retronym/ticket/7868

SI-7868 Account for numeric widening in match translation
SI-7859 Value classes may wrap a non-public member

We allow value class constructors to be non-public, so to be regular,
we should also allow the same for the param accessor.

This commit uses the 'makeNotPrivate' machinery to ensure that
the backend can generate the requisite unboxing calls.

This commit:

  - refactors the code that enforced the restrictions, improving
    a few error messages and positions. The remaining restrictions
    needed some rewording in light of this change.
  - allows value classes to have non-public, val parameters.
    private[this] / protected[this] are still disallowed as value
    classes don't have a concept of `this`, and because trying to
    accomdate then would complicate the implementation.

    This means that `class C(x: Int) extends AnyVal` is not allowed,
    the user still must write `private val x: Int` or `val x: Int`.
  - Outlaw `class C()()(val x: Int) extends AnyVal` to curtail any
    bugs that might lurk in such a formulation.

The tests:

  - Show that the privacy is respected in the typer phase, under
    joint and separate compilation. We don't want a repeat performance
    of SI-6601.
  - Show that code that needs compiler-generated unboxes works under
    both compilation scenarios
  - Checks that the remaining restrictions are enforced and well
    communicated.