Make enum classes comparable

#KT-3727 Fixed

compiler/testData/codegen/boxWithStdlib/enum/sortEnumEntries.kt

@@ -0,0 +1,16 @@
+import Game.*
+
+enum class Game {
+    ROCK
+    PAPER
+    SCISSORS
+    LIZARD
+    SPOCK
+}
+
+fun box(): String {
+    val a = array(LIZARD, SCISSORS, SPOCK, ROCK, PAPER)
+    a.sort()
+    val str = a.joinToString(" ")
+    return if (str == "ROCK PAPER SCISSORS LIZARD SPOCK") "OK" else "Fail: $str"
+}