Support single-underscore variable names partially

Currently only parameters of lambdas/function expressions
and destructuring entries are allowed

 #KT-3824 In Progress
 #KT-2783 In Progress

compiler/testData/diagnostics/tests/functionLiterals/underscopeParameters.txt

@@ -0,0 +1,5 @@
+package
+
+public fun bar(): kotlin.Unit
+public fun foo(/*0*/ block: (kotlin.Int, kotlin.String) -> kotlin.Unit): kotlin.Unit
+public fun foobar(/*0*/ block: (kotlin.Double) -> kotlin.Unit): kotlin.Unit