TypeTree printing modified (SI-8447)
SI-8609 Fix flattening of definitions and imports in quasiquotes

Quasiquotes allow to unquote trees with ..$ with block flattening
semantics to simplify composition:

  val onetwo = q"1; 2"
  val onetwothree = q"..$onetwo; 3" // same as q"1; 2; 3"

If there is no block it will be equivalent to $ unquoting:

  val one = q"1"
  val onetwo = q"..$one; 2" // same as q"1; 2"

But the inconsistency here is that currently only terms support
this single-element semantics. This commit extends this functionality
to also support definitions and imports. So that following code works:

  val q1 = q"val x = 1"
  val q2 = q"..$q1; val y = 2" // same as q"val x = 1; val y = 2"
SI-8494 Restore filtering javap output

Regressed in support for new delayedEndPoint, where it must
pick what to filter for.

`s/claas/klass/` and similar.
SI-8494 Javap filter includes specialized

When filtering javap output, include specialized versions
of methods. For anonfuns, in particular, the apply$sp is
the method of interest.
SI-8675 Avoid unreported error after second try using implicit view

This is specific to situations in which we first typecheck an
application `qual.m(arg)` against the method `m` directly provided
by `qual`, and then fall back to `implicitView(qual).m(arg)`.

Regressed in SI-3971 / 7fa77af, in which error reports were moved
to the innermost `Apply`, and the check for `errorInResult` was
accordingly changed to recurse through `Apply` trees.

Before that change, we did not fall back to using a view. After the
change, we do try a view. We retypecheck the arguments under the
`retyping` mode (see `tryTypedArgs`), but this doesn't seem to
be enough to avoid leaking the error typed nested trees from the
first try.

Here's an example from the enclosed test case:

    a.update(0, x[A]({new isString(true)}))
                                   `-- error typed

    refArrayOps(a).update(0, x[A]({new isString(true)}))
                             `                  `-- error type persists
                              `-- this tree is retypecked by tryTypedArgs

This commit changes `onError` to only proceed with the second
try if the retyped argument trees are error free.
SI-8675 Add another test case for swallowed type errors

As reported on scala-internals. After tightening up the treatment
of undetermined type parameters in SI-7944, the enclosed test
case no longer typechecks. And since the regression fixed in the
previous commit, the error was swallowed by the typechecker only
to be burped up by a crash in the backend.
SI-7577  Incorrect documentation: current default isn't Vector

Fixed documentation to specify List in four cases where it was wrong or missing.
SI-8638  Empty UnrolledBuffer hangs on prepend.

Tracked down bug to incorrect recursion in insertAll.  Fixed by adding a missing case (which incidentally will provide better performance when adding to the end of a block).

No specific tests, as this is caught by quasi-complete collections tests.
SI-5200  Incorrect advice for implementing mutable.Set in scaladoc

Fixed advice; it was already there in mutable.SetLike but a case sensitivity error kept it from appearing.
SI-8335  List.++ avoidably burns memory

Changed to check the identity of the CanBuildFrom instead of the identity of the generated builder to shortcut building.  Should reduce memory churn on ++ a little.
SI-7115  JMapWrapper.get can incorrectly return Some(null)

This isn't incorrect.  Trying to use a single-threaded interface in a concurrent context is supposed to break in various unpleasant ways.

Documentation has been added to encourage one to avoid wrapping a concurrent map in the generic wrapper (which assumes a single thread), and pointing out that synchronized maps do not maintain synchronization for non-atomic operations (including get).

More docs.
SI-8690 BufferedSource.mkString mistakenly skipped the first char.

mkString is overriden in BufferedSource for performance, but the
implementation always used the wrong reader. This seems to be a typo
(`allReader` is declared 5 lines earlier but never used, `charReader`
is used in its place).
Merge pull request #3849 from gourlaysama/wip/t8690

SI-8690 BufferedSource.mkString mistakenly skipped the first char.
SI-8292 report error when scaladoc fails to find doclet.
Merge pull request #3836 from gourlaysama/wip/t8292

SI-8292 report error when scaladoc fails to find doclet.
Merge pull request #3828 from retronym/ticket/8675

SI-8675 Avoid unreported error after second try using implicit view
Document SuperAccessors

Added comment giving an up-to-date overview of SuperAccessors
and how we might want to change it.
Merge pull request #3863 from adriaanm/rebase-3852

Document SuperAccessors
Merge pull request #3772 from densh/si/8609

SI-8609 Fix flattening of definitions and imports in quasiquotes
Merge pull request #3736 from VladimirNik/print-types-issue-2.11.x

SI-8447 fix TypeTree printing (2.11.x)