SI-7624 Fix -feature warnings and build with -feature

I added a language.existential import to LazyCombiner.scala which
should not be necessary, but causes a spurious warning otherwise:

    scala/src/library/scala/collection/parallel/mutable/LazyCombiner.scala:33:
    warning: the existential type
        scala.collection.parallel.mutable.LazyCombiner[_$1,_$2,_$3] forSome {
          type _$1; type _$2; type _$3 <: scala.collection.generic.Growable[_$1] with scala.collection.generic.Sizing },
    which cannot be expressed by wildcards, should be enabled by making the implicit value scala.language.existentials visible.
    if (other.isInstanceOf[LazyCombiner[_, _, _]]) {
                       ^

I created ticket SI-7750 to track this issue.
Formatting fixes for AnyVal

The files are not regenerated here, because additional fixes will
follow in the next commit.
SI-7624 Fix -Xlint warnings in AnyVal-related code

The changes are actually pretty small:
scala.language.implicitConversions is moved around so that it is only
emitted to the source file if there is an actual implicit conversion.
The rest of the diff are mostly the new generated source files
reflecting that change.
SI-7624 Fix a few remaining -Xlint warnings ...
in various places. This includes actors, compiler (mostly some new
macro parts) continuations, partest, scaladoc, scalap.
SI-7624 Replace new{Term,Type}Name with {Term,Type}Name
SI-7624 Fix -feature warnings in scala/tools/scalap

... and move scalap.scala.tools.scalap.scalax.rules to
scalap.scala.tools.scalap.rules now that all the Monad/Functor/
Applicatve/... stuff has been removed.
Whitespace fixes in scala/tools/scalap