Fix typo in documentation.
SI-7852 Test to show the status quo bytecode for "" == ...

Will be somewhat leaner after the next commit.
SI-7852 Omit null check for "".==

Although the same the code would be later optimized by -Yconst-opt,
we can offer the same lean byte code to those compiling without that
option by being more discerning when translating ==.

This helps people using bytecode based code coverage tools
such as jacoco that would emit "branch not covered" warnings
for the impossible null check.
SI-7852 Test to show status quo of for SomeModule.==

For which we can also elide the null check, and will in the
next commit.
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.
SI-7852 Omit null check for SomeModule.==

For the same reasons outlined in the previous commits.
SI-7852 Refactor null-elision tests to be more focussed

 - Directly count null checks, rather than diffing the textual
   bytecode of the entire method
 - Add a test to show that the LHS needs to be a direct module
   reference, not just a tree with a module type, to elide the
   null check.
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).
SI-7864 Harden "looks like an interpolated String" warning

We can't rely on the qualifier of an `Apply` having a non-null
symbol in general.
SI-7868 Account for numeric widening in match translation

Pattern match translation was unprepared for trees of the shape:

    (0: Short) match {
      case A.unapply(<unapply-selector>.toInt) <unapply> (_) => ()
      case _ => ()
    }

While a scrutinee is inelibigle for implicit views in order to
conform to the type of the extractor call, it is allowed to
weakly conform. In this case, the typechecker will add the
numeric widening with a `toInt` call.

This commit:

 - Changes treeInfo.Unapplied to recognize this tree shape
 - Changes spliceApply to recognize and preserve the widening
   when substituting the unapply selector with the binder
 - Tests reification of such pattern matches, which also depends
   on treeInfo.Unapplied.
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.