Exposed visibility checking, a set of exposed visibility tests, some test fixes

Effective visibility mechanism introduced.
Local is considered as public, java protected as Kotlin protected, java package private as Kotlin private.

compiler/testData/diagnostics/tests/enum/classObjectInEnumPrivate.kt

@@ -7,4 +7,4 @@ enum class E {
 fun foo() = E.values()
 fun bar() = E.valueOf("ENTRY")
 fun baz() = E.ENTRY
-fun quux() = <!INVISIBLE_MEMBER!>E<!>
+fun <!EXPOSED_FUNCTION_RETURN_TYPE!>quux<!>() = <!INVISIBLE_MEMBER!>E<!>