Enabling commit for interactive/scaladoc modules.

This is a non-behaviorally-changing setup commit which
re-routes bits of code through avenues which can more easily
be influenced by subclasses of Global.
Moved scaladoc sources into separate directory.

This change is not externally visible. It moves the scaladoc
sources into src/scaladoc and adds an ant target for building
them. The compilation products are still packaged into
scala-compiler.jar as before, but with a small change to
build.xml a separate jar can be created instead.
Moved interactive sources into separate directory.

As with the preceding commit, this has build-internal
effects only.
Teach partest the magic of abstraction.

Some new partest abilities which were necessary to deal with
additional standard jars. These new abilities aren't yet put
to the test because scaladoc and interactive are still going
into the compiler jar.

No longer need each jar or classes directory be named
directly for partest to find them.
Give partest its own classpath in build.xml.

Separate from (and larger than) pack.classpath. Then take
the opportunity to lower the comic/tragic level of duplication
in build.xml.
Give interactive tests their own target.

% ant test.interactive
Moved scaladoc code into src/scaladoc.

This leverages the preceding several commits to push scaladoc
specific code into src/scaladoc. It also renders some scanner
code more comprehensible.
Moved interactive code into src/interactive.

As with scaladoc, pushes presentation compiler specific
code into its separate source area.
Eliminated all forInteractive/forScaladoc uses.

This is the commit which brings it all together. The booleans
forInteractive and forScaladoc are now deprecated and are not
inspected for any purpose. All behavioral changes formerly
accomplished via tests of those flags are embodied in the globals
built specifically for those tasks.