Rewrite Obj-C built-in classes from Java to Kotlin

- ant 'runtime' target now builds kotlin-objc-runtime.jar with Objective-C
  built-ins for JVM
- all classes in jet/objc were rewritten to Kotlin except jet.objc.Native which
  uses native Java methods, which aren't possible to implement in Kotlin yet
- lots of testData for objc-resolve were changed since now loaded Kotlin
  classes have invisible fake descriptors for private members in superclasses:
  JDR doesn't look at private Java members at all
Move objc/ directory out of compiler/ to top-level
Move KotlinNative runtime to objc/runtime.objc/
Pack libKotlinNative.dylib into kotlin-objc-runtime.jar