Fix #211: java.util.Formatter does not support `n` conversion
Fix #228: Add primitive js.debugger() mapping to debugger statement.
Merge pull request #229 from sjrd/equivalent-to-debugger

Fix #228: Add primitive js.debugger() mapping to debugger statement.
Merge pull request #230 from sjrd/fix-n-format

Fix #211: java.util.Formatter does not support `n` conversion
Add Scala.js specific scala.Symbol implementation

The cache that scala.Symbol uses to maintain symbol instances depends on
java.util.WeakHashMap and java.util.concurrent.locks.ReentrantReadWriteLock
which are neither supported and don't make sense for JavaScript.

Replace scala.Symbol's cache implementation with a simple js.Dictionary
backed cache to fix runtime issues, such as:

    [error]     TypeError: org.mozilla.javascript.Undefined@1221f81 is not a function, it is undefined. in
    [error] @file:///.../scala-js/scalalib/source/src/library/scala/Symbol.scala:48
    [error] @file:///.../scala-js/scalalib/source/src/library/scala/Symbol.scala:34
Fix #225: provide an equivalent of JS' `typeof x`.

It is introduced as `js.typeOf(x)`.
Merge pull request #236 from sjrd/equivalent-of-typeof-in-package

Fix #225: provide an equivalent of JS' `typeof x`.
Merge pull request #234 from jonas/js-symbol-cache

Add Scala.js specific scala.Symbol implementation
Add implementation for String.equalsIgnoreCase

Also adds missing tests for String.compareToIgnoreCase.

Fixes #233
Merge pull request #235 from jonas/string-equalsignorecase

Add implementation for String.equalsIgnoreCase