SI-6811 Remove scala.annotation.serializable

Every usage of it has been eliminated in earlier commits,
so the source file can finally be removed, too.
SI-6811 Remove usages of scala.annotation.cloneable

The source file itself will be removed later,
because the compiler seems to need it for boot-strapping.
SI-6811 Remove deprecated constructors
SI-6811 Remove primitive widenings and /:\
SI-6811 Remove scala.collection.mutable.ConcurrentMap
SI-6811 Remove the scala.util.grammar package
SI-6811 Remove parts of scala.concurrent not needed by scala.actors
SI-6811 Remove deprecated elements in scala.collection
SI-6811 Misc. removals in util, testing, io, ...
SI-6811 Remove the scala.annotation.target package
SI-6811 Remove scala.ScalaObject
SI-6811 Remove scala.xml.include.sax.Main
SI-6811 Move scala.util.{automata,regexp} ...
... to scala.xml.dtd.impl and make it private[dtd]
Merge pull request #1921 from soc/SI-6811-removals

SI-6811 Scheduled removal of deprecated items for 2.11
Merge pull request #1939 from soc/SI-6811-moves

SI-6811 Move scala.util.{automata,regexp} ...
SI-2577, SI-6860: annotation type inference.

This is less than ideal:

  scala> class Bippy[T] extends annotation.StaticAnnotation
  defined class Bippy

  scala> def f: Int @Bippy = 5
  f: Int @Bippy[T]

Turns out we can infer such types. Now it says:

  scala> def f: Int @Bippy = 5
  f: Int @Bippy[Nothing]

This should put to rest many an issue with parameterized
annotations.
SI-5182, no position on annotation error.

Now there's a position on the synthetic "value" Ident.
SI-6083, misleading annotation error message.

When an implicit conversion causes an apparently constant
argument not to be constant, show the conversion, not the
constant.
Added test for untested nested annotation restriction.
Renamed methods to be less ambiguous in intent.

isNamed    => isNamedArg
isIdentity => allArgsArePositional
nameOf     => nameOfNamedArg

Moved mkNamedArg into TreeGen.