SI-6448 Collecting the spoils of PartialFun#runWith

Avoids calling both `isDefinedAt` and `apply`. This pathological
case that would benefit the most looks like:

  xs collect {
    case x if {expensive(); true} => x
  }

The typical change looks like:

-    for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
+    foreach(pf.runWith(b += _))

Incorporates feedback provided by Pavel Pavlov:

  https://github.com/retronym/scala/commit/ef5430

A few more opportunities for optimization are noted in the
`Pending` section of the enclosed test. `Iterator.collect`
would be nice, but a solution eludes me.

Calling the guard less frequently does change the behaviour
of these functions in an obervable way, but not contravene
the documented semantics. That said, there is an alternative
opinion on the comment of the ticket:

  https://issues.scala-lang.org/browse/SI-6448
Merge pull request #1574 from jsuereth/merge-2.10.0

Merge 2.10.0-RC2 into 2.10.x
SI-6616 Check that unsafe operations are only called on the presentation compiler thread.

The method that checks the actual constraint is @elidable, expecting it to be used
for nightly builds but stripped-off in release builds. This way we don't lose any
performance, but 'fail-fast' in IDE nightlies.

This assumes that release builds will have at least `-Xelide-below ASSERTION`, but
this pull request does not do that.
comment / question in typers
SI-6539 Annotation for methods unfit for post-typer ASTs

Motivated by the `.value` method in the SBT task-syntax branch,
which should only be called within the context of the argument
to a setting initialization macro.

The facility is akin to a fatal deprecation.
Optimize primitive Array(e1, ..., en)

Expands an existing optimization for reference arrays to
apply to primitives, as well.

Fixes one aspect of SI-6247.
More principled tree copying.

Canonical > home-spun.
New starr based on 4f98d50bc2 .

Contains the extension method naming change, in the
interests of unbreaking the sbt build for a while.
Refine @compileTimeOnly

 - Don't default the message, and show it exclusively.
 - Fix cut-and-pasto in the @since tag
 - Be tolerant if the annotaion class is missing, as seems to
   have been the case compiling the continuations plugin.
 - s/\t/  / in the test file to show the errors are positioned
   correctly.
 - Use defensive getOrElse
show developer guidelines on opening pull request

Includes "Improvements and typo fixes to CONTRIBUTING.md" by @heathercmiller
as well as feedback from @retronym.
Remove hostile code from explicitouter.

If that's the $outer accessor, what's that being created
in newOuterAccessor? Sketchy, sketchy business.
Associate correct names to e-mails, correct or not

This is used by git log to produce names with certain formats, and
is used by the release notes tool as well. Helpful if you have commits
with Author not set correctly, as did I.

I'm also including Aleksandar Prokopec and his friend Aleksandar Pokopec,
as well as Pavel Pavlov, both of whom have commits appearing under more
than one name.

I'm not including others who have not set a full name, but don't have
commits appearing under more than one name.
fix t2318.scala
Update tools/epfl-publish

Currently, during each Scala nightly build, the epfl-publish script rsyncs the resulting dists/archives to the repository machine (chara).

Now, as a result of a change introduced a while back, dists/archives/ now also contains a symbolic link, created at the end of the build when the targets "pack-archives.latest.*" are invoked (in src/build/pack.xml). That was introduced in:

scala/scala@506bcfe71c93160ebfa0ca9b8b170b4b54e844e9
scala/scala@cb99853c8655686dae1288cbcd44a42cf1ea6609

This link, created in dists/archives/, is copied over as-is at the end of the rsync to chara by epfl-publish. On chara, however, the link points to an invalid target (the path is absolute).

Separately, the repository directory on chara is rsync'd every 30 minutes over to the machine that serves www.scala-lang.org, via cron. Rsynch finds that the link target does not exist, and generates an email with the crontab log, which is then duly sent to a system mailbox. Every 30 minutes. Since March. Needless to say, the mailbox is pretty large by now.

The fix is trivial, but this needs to be included in all the branches that are tested during the nightly. Since RC2 has just been cut, and the code frozen, I'm not sure how this change can be included without disruption; therefore, I'll just send a pull request on 2.10.0-wip, and let Josh/Paul take the appropriate steps.
Fix SI-6637 (misoptimization in erasure)

Move the optimization one level deeper so the expression
being tested with isInstanceOf is always evaluated.
Fix type of the custom `ClassTag` in `PatternMatching.scala`

In fb315772 custom ClassTags were introduced to optimize array
creation in hot places. The idea was that if `Array[T]` is allocated
through `ClassTag[T]` (which is essentially a factory for Array[T])
we would introduce a custom class implementing `ClassTag[T]` interface
and would have specialized array allocation instruction instead of
having reflective call as it's being done with default (compiler
synthesized) implementation of `ClassTag[T]`.

In case of `PatternMatching.scala` I made a mistake of providing
`ClassTag[Array[Clause]]` instead of `ClassTag[Clause]` so that value
would never be used and compiler still would resolve implicit through
default mechanism. This has been discovered thanks to @paulp's work
on unused value detection.

Review by @paulp.
Merge pull request #1591 from paulp/new-starr

New starr based on 4f98d50bc2 .
Merge pull request #1595 from paulp/explicit-outer-fix

Remove hostile code from explicitouter.
Hardened JavaMirrors against linkage errors.

After running into a ClassCircularityError and following it
back to this, I simplified the method to route all linkage
errors the same way. And added logging.
Minor tweaks in Types/Scopes.

All methods to do with handling imports more uniformly and early
filtering of symbols which cannot be imported. Also make TypeBounds
treat a Wildcard in lower or upper bounds as an empty bound, so we
don't see all these method signatures like

  def f[T >: ? <: ?]

because that's not helpful.