Split Library.kt into several files

For better readbility and discoverability. Also rename String.compareTo
parameter to "other", since that is the name of parameter of other compareTo's

core/builtins/native/kotlin/Throwable.kt

@@ -0,0 +1,9 @@
+package kotlin
+
+public open class Throwable(message: String? = null, cause: Throwable? = null) {
+    public fun getMessage(): String?
+
+    public fun getCause(): Throwable?
+
+    public fun printStackTrace(): Unit
+}