Introduce experimental -Xuse-javac compilation mode

In this mode, javac AST and Symbol files are used during
Kotlin compilation instead of PSI / binary stuff.
Later, they are reused for Java file compilation.
javac in this mode is integrated into kotlinc.

compiler/testData/compileKotlinAgainstJava/AbstractEnum.java

@@ -0,0 +1,12 @@
+package test;
+
+public enum AbstractEnum {
+
+    ONE {
+        @Override
+        String getString() { return null; }
+    };
+
+    abstract String getString();
+
+}