Added a Swing PopupMenu wrapper
Added a Swing ColorChooser wrapper
Fixes SI-6170: issue with dragging scaladoc splitter over central iframe
Scaladoc knows the package structure of the libraries,
so don't include them in external documentation setting.
Changes Tree and Type members from vals to defs.

Explanatory email:

The reflection API defines a great many abstract vals. I would
like these all to be defs. I'm sending a pull request to that end.

Reasons: for starters, they should default to being defs. It's a
decision to use vals for which one should have to supply reasons.
The reason for THAT is that defs can be implemented with vals, but
not vice versa.

Why does this matter? I can't find my long writing on the subject
of TypeRef. In short, we waste a huge amount of memory on its
fields, because given the way TypeRef is defined, each one demands
a pre, a sym, and an args. Except that somewhere between 1/3 and
1/2 have prefix "NoPrefix", and somewhere between 1/3 and 1/2 have
args "Nil". We know it at creation time, but we give every typeref
the whole field anyway.

At present there's no way to fix this which has acceptable
performance - i.e. custom subclasses save us lots of memory, but
are too much slower for having to use an extractor - but there's
no reason we should have to choose, and I fully expect to fix it
eventually. Let's not make that fix into a breaking change by
abstractly defining "pre" and "args" as field-requiring vals.
Remove unneeded calls to substring()
SI-6526 Tail call elimination should descend deeper.

It wasn't traversing into Select nodes nor into the receiver of
a tail call.
Closes SI-6358. Move accessor generation for lazy vals to typers.

Until now lazy accessors were handled somehow special because their symbol was created in typers but the corresponding tree was only added in Refchecks. This irregularity caused serious problems for value classes. Also it now looks just better when lazy value is treated in a similar way as other fields.

I needed to adapt reifier so that it handles the new implementation correctly. Previously it had to recreate lazy val only by removing defdef and renaming. Now we basically need to recreate lazy val from scratch.

There is one minor change to cps plugin but that is still fine because lazy vals were never really part of the transformation.

Some range positions needed to be fixed manually. We could do it at the creation time but that would require a lot more "if (symbol.isLazy)" conditions for MethodSyntheis and Symbol/Tree creation and would just unnecessary complicate api. If someone has a better idea, please speak up. Range positions changes were necessary because previously accessors were created at refchecks and they weren't checked by validator (even though they were wrong).

This commit removes lazy val implementation restriction introduced for 2.10.0.
(cherry-picked from 981424b)
Added one more test for SI-6358
Incorporated changes suggested in code review
Crash on missing accessor (internal bug in the lazy vals implementation) instead of trying to recover from the bug
Fix for SI-6537, inaccurate unchecked warning.

I found a more direct expression of the unchecked logic,
which should be much easier for others to verify.  But the
bug being fixed here is that the unchecked checking happens
too early, and the sealed children of a symbol are not yet
visible if it is being simultaneously compiled.
avoid single-art assert where harmful in duration-tck
Merge pull request #1498 from paulp/defs-not-vals

Changes Tree and Type members from vals to defs.
Merge pull request #1403 from ingoem/topic/swing

Adds Swing wrappers for ColorChooser and PopupMenu
Merge pull request #1480 from ingoem/topic/scaladoc

Fixes SI-6170: issue with dragging scaladoc splitter over central iframe
Merge pull request #1501 from vigdorchik/doc_strings

Remove unneeded calls to substring()
Merge pull request #1510 from rkuhn/wip-duration-tck-one-arg-assert

avoid single-arg assert where harmful in duration-tck
Merge pull request #1509 from paulp/issue/6537

Fix for SI-6537, inaccurate unchecked warning.
Merge pull request #1508 from hubertp/2.10.x-issue/6358

Backport commits that fix SI-6358 from master