Fixes SI-6170: issue with dragging scaladoc splitter over central iframe
SI-6440: Revert change to `TraversableLike.filterNot`

Commit df9f470f14262b9b1002f022c2620d8c38835805 introduced
a change to `TraversableLike.filterNot` which broke Stream
implementation that does override `filter` implementation
but does not override `filterNot` implementation. This shows
clearly that reusing code for strict and non-strict collections
is very problematic.

Added a test-case covering this problem.

Closes SI-6440.

Review by @retronym.
Deprecated instrumentation API

The instrumentation logic needed by the Scala IDE Worksheet is currently part
of the Scala project, but it doesn't need to be.  I already have a PR ready for
completely removing the instrumentation logic, but I considered it too risky at
this point for 2.10.0 release (an oversight can lead to the impossibility of
running the worksheet with Scala 2.10.0).

For the moment, I believe it's better to deprecate the whole instrumentation
API in 2.10.0, and the PR for removing the instrumentation logic will target
2.10.1 or 2.11.0.

Besides deprecating the instrumentation API, this commit also raised visibility
of `interruptsEnabled` member in `Global`.  This change alone is sufficient for
moving the instrumentation logic outside of the compiler, and it is needed
because the Presentation Compiler thread should never be interrupted while
instrumenting a source.

This commit is related to SI-6458
Merge pull request #1483 from gkossakowski/SI-6440

SI-6440: Revert change to `TraversableLike.filterNot`
Fixed SI-6505. Respond to ask calls by immediate failure even after compiler shutdown.

When the compiler is asked to shutdown, it may still have items on the working queue, and more can be added by clients in other thread that don't *know* the compiler is down yet. These requests were never serviced, leading to deadlocks or timeouts.

review by @odersky, @hubertp
SI-6099 - Scaladoc for scala.concurrent incomplete

This is a rebase and resubmission of @phaller's pull
https://github.com/scala/scala/pull/1485
With the reviewers' comments additionally addressed
Merge pull request #1488 from dotta/topic/deprecated-instrumentation-api

Deprecated instrumentation API
SI-6453 Documentation links for @switch are broken
Merge pull request #1486 from heathermiller/issue/6099

SI-6099 - Scaladoc for scala.concurrent incomplete
Fix for SI-6499, regression in type inference.

I can't do any better than a reproduced comment:

For some reason which is still a bit fuzzy, we must let Nothing
through as a lower bound despite the fact that Nothing is always
a lower bound. My current supposition is that the side-effecting
type constraint accumulation mechanism depends on these subtype
tests being performed to make forward progress when there are
mutally recursive type vars. See pos/t6367 and pos/t6499 for the
competing test cases.
Merge pull request #1490 from paulp/issue/6499

Fix for SI-6499, regression in type inference.
Merge pull request #1487 from dragos/issue/fix-6505

Fixed SI-6505. Respond to ask calls by immediate failure after compiler shutdown.
SI-6487 Scaladoc can link to inner classes
SI-6495 Scaladoc will pick up group from owner
SI-6501 Scaladoc will correctly link to @templated

members
SI-6155 Scaladoc @template diagrms
SI-6509 Correct @template owners
Merge pull request #1491 from VladUreche/topic/scaladoc2

Scaladoc bugfixes for reflection
docs for reflection and macros
reflection docs improvements and moves to doc page