SI-5314 - CPS transform of return statement fails

Enable return expressions in CPS code if they are in tail position. Note that tail returns are
only removed in methods that do not call `shift` or `reset` (otherwise, an error is reported).

Addresses the issues pointed out in a previous pull request:
https://github.com/scala/scala/pull/720

- Addresses all issues mentioned here:
  https://github.com/scala/scala/pull/720#issuecomment-6429705

- Move transformation methods to SelectiveANFTransform.scala:
  https://github.com/scala/scala/pull/720#commitcomment-1477497

- Do not keep a list of tail returns.

Tests:
- continuations-neg/t5314-missing-result-type.scala
- continuations-neg/t5314-type-error.scala
- continuations-neg/t5314-npe.scala
- continuations-neg/t5314-return-reset.scala
- continuations-run/t5314.scala
- continuations-run/t5314-2.scala
- continuations-run/t5314-3.scala
Replace CheckCPSMethodTraverser with additional parameter on transformer methods

Other fixes:

- remove CPSUtils.allCPSMethods
- add clarifying comment about adding a plus marker to a return expression
Add missing cases in tail return transform

Disabled warnings that no longer apply because of tail returns.
Add several test cases.
Revert "Add missing cases in tail return transform"

This reverts commit 8d020fab9758ced93eb18fa51c906b95ec104aed.
Simplify the adaptation of types of return expressions

Add `adaptTypeOfReturn` hook to `AnnotationCheckers`.
Move adaptation of types of return expressions from `addAnnotations`
to `typedReturn` via `adaptTypeOfReturn` hook.

This resolves an inconsistency where previously types could have
a plus marker without additional CPS annotations. This also adds
additional test cases.
Improve doc comment on adaptTypeOfReturn in CPSAnnotationChecker
SI-6170 Revert #456 "Upgrade jQuery from 1.4.2 to 1.7.2"

This reverts commit b6c0e4478616a1252d65754a40c5dcbfc6554b36 because it caused SI-6170,
after this revert, the left "search" panel of scaladoc should be resizable again.
SI-4857 fixes showall/hideall Scaladoc interface bug
Automatically highlight and scroll to linked-to members
Fix for SI-6344, value class generic signatures.

Value classes mostly erase to the erasure of the
underlying type.  Not everything in the checkfile
looks correct, but I know from experience I can
spend the rest of my life poking at erasures, so
let's try to book some progress.
SI-6380 #1 Add @throws[Exception]

This change allows an additional notation of the @throws annotation:

  Old-style: @throws(classOf[Exception])
  New-style: @throws[Exception]

The optional String argument moves @throws in line with @deprecated,
@migration, etc. and prevents confusion caused by the default inheritance
of ScalaDoc comments and the non-inheritance of annotations.

  Before: /** This method does ...
            * @throws IllegalArgumentException if `a` is less than 0. */
          @throws(classOf[IllegalArgumentException])
          def foo(a: Int) = ...

  Now:    /** This method does ... */
          @throws[IllegalArgumentException]("if `a` is less than 0")
          def foo(a: Int) = ...

ScalaDoc @throws tags remain supported for cases where documentation of
thrown exceptions is needed, but are not supposed to be added to the
exception attribute of the class file.

In this commit the necessary compiler support is added.
The code to extract exceptions from annotations is now shared instead
of being duplicated all over the place.

The change is completely source and binary compatible, except that the code
is now enforcing that the type thrown is a subtype of Throwable as mandated
by the JVM spec  instead of allowing something like @throws(classOf[String]).

Not in this commit:
  - ScalaDoc support to add the String argument to ScalaDoc's exception list
  - Adaption of the library
minor cleanup for reflection
SI-6412 fixes leaks in Types.uniques

This is the most blatant leak in reflection. There are others, but their impact
is much smaller, therefore we'll fix them later, after 2.10.0-final.

For more information, see https://issues.scala-lang.org/browse/SI-6412 and
http://groups.google.com/group/scala-internals/browse_thread/thread/eabcf3d406dab8b2
SI-6412 alleviates leaks in toolboxes

Turns importer caches into fully weak hash maps, and also applies
manual cleanup to toolboxes every time they are used.

It's not enough, because reflection-mem-typecheck test is still leaking
at a rate of ~100kb per typecheck, but it's much better than it was before.
We'll fix the rest later, after 2.10.0-final.

For more information, see https://issues.scala-lang.org/browse/SI-6412 and
http://groups.google.com/group/scala-internals/browse_thread/thread/eabcf3d406dab8b2
fixes mirrorThatLoaded in JavaMirrors

`mirrorThatLoaded(sym: Symbol): Mirror` in JavaMirrors used to iterate over
`lazy val mirrors = new WeakHashMap[ClassLoader, WeakReference[JavaMirror]]()`
to find out what mirror has loaded a certain symbol.

It worked okay until yesterday when I noticed failing tests, which crashed
when weak references in mirrors were dereferenced with get.get. Apparently
some mirrors were collected, and the logic in JavaMirror didn't account for
that possibility.

When fixing this bug, I noticed that mirrors can become unreachable even
if there are still reachable symbols created by those mirrors. That doesn't
make sense, therefore I fixed this bug as well by introducing a strong ref
from root symbols to the enclosing mirror. Therefore, any active symbol
will have a strong reference to the enclosing mirror by the virtue of the
owner chain.
distinguishes flag-agnostic completers

At times it's useful to know whether a lazy type can change
the flags of the underlying symbol or not.

If the completer is flag-agnostic, this means that we can safely
use flag-inspection facilities such as hasFlag and isXXX tests
without fear of looking into not yet initialized data.
Merge pull request #1385 from scalamacros/ticket/6412

SI-6412 some fixes for reflection leaks
Fixed instrumentation code so that it can deal with:

1. leading imports: object sheet { import math; … }
2. trailing objects: object sheet { … } object other { … }

Review by @dragos
SI-6305 fix.
Support for scala.concurrent for the ActorRef.

Review by @phaller