New enum syntax: Short constructor syntax introduced for entries, optional commas between entries, semicolon after entries. #KT-7605 Fixed.

Grammar changed accordingly.
Semicolons prohibited after an entry except the last one.
Only one initializer is allowed per entry.
EnumReferenceExpression AST node introduced.
Some tests fixed, a pair of new tests written. Kotlin code inside project fixed.
Formatter and intendation tests fixed accordingly.
Stub version is incremented.

compiler/testData/codegen/box/classes/kt2626.kt

@@ -5,6 +5,6 @@ fun box() = Context.OsType.OK.toString()
 object Context
 {
         public enum class OsType {
-                WIN2000; WINDOWS; MACOSX; LINUX; OTHER; OK
+                WIN2000, WINDOWS, MACOSX, LINUX, OTHER, OK;
         }
 }