Fixes SI-6337 by disallowing nested value classes.

It seems for the moment too hard to allow this, and the functionality to have value classes wrap other value classes does not seem essential.
Fixed comment.
enable integer multiplication/divison on FiniteDuration, see SI-6389

- without this "2.seconds * 2" will not return FiniteDuration but
  Duration
- added test case verifying this behavior
- matches normal arithmetics: integers throw on div-by-zero while
  doubles yield infinity; extended here to include overflow protection
  on integer multiplication
existentially typed expansions now work fine

If one tries to compile the following code with the parent of this commit:

  ru.reify(new Object().getClass)

then the following error will occur:

  Test.scala:2: error: type mismatch;
    found   : $u.Expr[Class[_ <: Object]]
    required: reflect.runtime.universe.Expr[Class[?0(in value <local Test>)]]
              where type ?0(in value <local Test>) <: Object
    ru.reify(new Object().getClass)
            ^

This happens because macro expansions are always typechecked against the
return type of their macro definitions instantiated in the context of expandee.

In this case the expected type contains skolems which are incompatible
with wildcards in the type of the expansion.

I tried all the incantations I could think of - without any success.
Luckily I met Martin who pointed me at the same problem solved in adapt
(see the diff w.r.t Typers.scala).
test case closes SI-5418

Now, when the existential reification bug is fixed, I've been able
to take a look at SI-5418, and, apparently, the problem with importers
has fixed itself during these 9 months of the bug being active.
SI-6336 Now also catches return types

As Mark's comments on SI-6336 shows, we also need to disallow value classes
as return types of structural types.
Fixes SI-6305 scala.tools.nsc.io split between jars.

* migrates scala.tools.nsc.io portions into scala.reflect.io
* marks all classes in scala.reflect.io experimental/internal
* rewires src/reflect to use new io locations
* creates forwarders in scala.tools.nsci.io package object.
Adds OSGi support / tests to Scala.  Fixes SI-5822.

* Adds BND manifest generation to the build.
* Adds OSGi pax-exam testing infrastructure
* Adds simple OSGi verification test for bundle resolution.
* Modifies distribution to use bundles.
Adds very simplistic reflection in OSGi test.   Provides the framework
to discover important reflection bugs in OSGi containers.
improve performance of integer multiplication overflow check on Duration

- also rename divisor arguments to “divisor”
- and add a scalacheck for multiplication overflow detection
Additional OSGi tests.

* Ensure scala-library can be resolved on its own, and with sun.misc.Unsafe usage.
* Ensure reflection works without scala-compiler.jar
* Ensure ToolBox's can see all classes necessary when evaluating expressions.
* Cleanup test helper for filtering in/out bundles.
move Duration (incl. DSL) into scala.concurrent.duration package

so that the full package can be imported naturally:

import scala.concurrent.duration._

will give you all the types (Duration, FiniteDuration, Deadline) and the
DSL for constructing these.
Fix problem with names encoding in scalap.

The refactoring performed in 020053c321 made use of naming encoding
more consisted but introduced a regression in scalap. The problem
is that the old encoder that scalap had didn't escape any characters
that were not included in its opcode list.

`NameTransformer` performs full encoding so it also encodes dots
that are being used as separators for packages. Therefore, in order
to retain the old behaviour we need to split the name by dots before
feeding each fragment to `NameTransformer`.

Review by @paulp.
Adjustments to scala.concurrent.duration.

More use of implicit classes and value classes; aliased units to
make importing TimeUnit and TimeUnit._ unnecessary; placed some
classes in their own files because "the unit of compilation is
the file" and we shouldn't bundle more than necessary; fixed some
examples.
Error message improvement for SI-6336.

Position error messages about structural type members at the
problematic parameter or type.
SI-6394 fixes macros.Context.enclosingClass

Previously I used typer.context.enclClass, but it seems to do something
completely unexpected, so I switched to manual context traversal.
Fix for loud test.
SI-5943 toolboxes now autoimport Predef and scala

Previously tb.typeCheck used default typer, which builds upon NoContext.
Changing the context to analyzer.rootContext(NoCompilationUnit, EmptyTree)
fixed the missing imports problem.

Unfortunately this doesn't help in cases like "math.sqrt(4.0)" because of
https://issues.scala-lang.org/browse/SI-6393. But anyways I'm adding
this test case to pending.
some small remaining fixes

- added test for “span” and “fromNow” qualifiers
- make those actually work even when there is an expected type
- add ScalaDoc to them
- verify (and fix) conversion Deadline -> FiniteDuration
- also make Int * Duration => FiniteDuration work (and test it)
don't try to create tags w/o scala-reflect.jar

Since recently type tags have relocated to scala-reflect.jar,
meaning that they are no longer always on library classpath.

In the compiler we do have code that generates type tags, and this code
is bound to fail if scala-reflect.jar isn't there.

I though this wouldn't be a problem, because type tag materialization
is only going to be triggered by users explicitly requesting a type tag.

That's generally true, but I overlooked a corner case. Since we provide
manifest <-> type tag compatibility, manifest lookup can sometimes trigger
tag lookup, which might result in tag synthesis, which blows up like this:
http://groups.google.com/group/scala-internals/browse_thread/thread/166ce4b71b7c46bb

This commit also ensures that type tag generation/interop doesnt sneak into the
code of the libraries that don't have scala-reflect.jar on their classpath.
For details refer to the discussion at scala-internals:
http://groups.google.com/group/scala-internals/browse_thread/thread/72f6ce3010f4d8