SI-6449 Adds version arg to @deprecated usages (non-compiler sources)
Fix incomplete version strings (2.10 -> 2.10.0)
SI-6442 - Add ActorDSL object for actor migration kit

Removes MigrationSystem, since ActorDSL replaces it.
Revert "SI-4881 infer variance from formals, then result"

This reverts commit 5c5e8d4dcd151a6e2bf9e7c259c618b9b4eff00f.
Test case for SI-6311.

This covers the situation which broke in 5c5e8d4dcd,
reverted in the previous commit.
Fixes deprecation annotations for 2.10.0
Fix StringContext documentation.

It doesn't call "new", as I discovered after some head
scratching.
Merge pull request #1424 from soc/SI-6449

SI-6449 Adds version arg to @deprecated usages (non-compiler sources)
Merge pull request #1428 from paulp/issue/6311

Issue/6311
Merge pull request #1435 from paulp/stringcontext-doc

Fix StringContext documentation.
fixes a bug in a weak cache in runtime reflection

Entries in SynchronizedTypes.uniques could previously be garbage collected
in-between a successful call to contains and an actual cache lookup.

The patch could be a one-liner, but I don't want to use HOFs
in this function, whose prototype is a hotspot in the compiler.

Also the fix doesn't touch scalac in any way. It only applies to
reflective universes that provide runtime reflection functionality.
Improved the `scala.language` documentation

Also corrected the links in the library rootdoc.

**Note: We need to fast track this commit so it reaches master in the
next 12 hours, before we generate the next nightly docs.**

Review by @odersky
Merge pull request #1425 from phaller/issue/6442

SI-6442 - Add ActorDSL object for actor migration kit
Merge pull request #1440 from VladUreche/issue/language-doc

Improved the `scala.language` documentation
Merge pull request #1434 from jsuereth/fix/SI-6449

Fixes deprecation annotations for 2.10.0
Merge pull request #1439 from scalamacros/topic/reflective-uniques

fixes a bug in a weak cache in runtime reflection
SI-6436 Handle ambiguous string processors

Before, we got in an inifinite loop by chasing
the error typed result of adaptToMemberWithArgs.

One point of befuddlement remains: why did t6436 and t6436b
behave differently before this change?
Revised restrictions for value classes and unversal traits

and brought compiler in line with them. One thing we can accept IMO are nested
classes (nested objects are still a problem). In fact, it makes no sense to
exclude nested classes from value classes but not from universal traits. A class
nested in universal trait will becomes a class nested in a value class by
inheritance. Note that the reflection library already contains a universal trait
with a nested class (IndexedSeqLike), so we should accept them if we can.
Fixed problem in SI-6408

Fixed problem reported in comment, where inner classes of value classe caused a compiler crash.
Put more implementation restrictions on value classes.

Nested objects, classes and lazy vals are disallowed at any
nesting level in value classes; e.g. lazy vals local to a
method defined in a value class. There are still allowed in
universal traits.

This is a temporary, implementation restriction that is planned
to be addressed in future releases of Scala. Error messages has
been updated to communicate that intent.

Moved tests for SI-5582 and SI-6408 to pending folder. They have
to stay there until implementation restrictions are addressed.

Closes SI-6408 and SI-6432.

Review by @odersky, @harrah and @adriaanm.