SI-5784 Scaladoc: {Abstract,Alias} type templates

Normally scaladoc won't generate template pages for anything other than
packages, classes, traits and objects. But using the @template
annotation on {abstract,alias} types, they get their own page and take
part as full members in the diagrams. Furthermore, when looking for the
companion object, if a value of type T is in scope, T will be taken as
the companion object (even though it might be a class)

All templates, including types are listed on the left navigation pane,
so now adding @template to String can get scaladoc to generate (a
no-comments) page for java.lang.String.

The {abstract, alias} type icons need to be updated -- I just took the
class icons and added a small x to them -- but they shoud be something
else (maybe an underscore?)i

TO USE THIS PATCH:
<pre>
/** @contentDiagram */ // tells scaladoc to create a diagram of the
                       // templates contained in trait Base
trait Base {
  /** @template */ // tells scaladoc to create a page for Foo
  type T < Foo
  trait Foo { def foo: Int }
}

/** @contentDiagram */
trait Api extends Base {
  /** @template */
  override type T <: FooApi
  trait FooApi extends Foo { def bar: String }
}
</pre>

1 files changed, 1 insertions, 0 deletions

diff --git a/test/scaladoc/run/SI-5784.check b/test/scaladoc/run/SI-5784.check
new file mode 100644
index 0000000000..619c56180b
--- /dev/null
+++ b/test/scaladoc/run/SI-5784.check
@@ -0,0 +1 @@
+Done.