Initial infrastructure and hello world for the Scala.js back-end.

The Scala.js back-end can be enabled with the `-scalajs`
command-line option. Currently, it adds one phase to the pipeline,
which emits .sjsir files from trees.

A sandbox project `sjsSandbox`, in `sandbox/scalajs/`, can be used
to easily test Scala.js compilation. One can run the `main()`
method of the `hello.world` object with

  > sjsSandbox/run

The back-end only contains the bare mimimum to compile the hello
world application in the sandbox. Anything else will blow up
(for example, primitive method calls). It is a work-in-progress.

1 files changed, 15 insertions, 0 deletions

diff --git a/sandbox/scalajs/hello.scala b/sandbox/scalajs/hello.scala
new file mode 100644
index 000000000..bd4aa8cc5
--- /dev/null
+++ b/sandbox/scalajs/hello.scala
@@ -0,0 +1,15 @@
+package hello
+
+import scala.scalajs.js
+
+trait MyTrait {
+  val x = 5
+  def foo(y: Int) = x
+}
+
+object world extends js.JSApp with MyTrait {
+  def main(): Unit = {
+    println("hello dotty.js!")
+    println(foo(4))
+  }
+}