Support for "a is Function".

tests/language/language-leg.status

Index: tests/language/language-leg.status
===================================================================
--- tests/language/language-leg.status	(revision 5320)
+++ tests/language/language-leg.status	(working copy)
@@ -18,7 +18,6 @@
 CTConst3Test: Fail # CompileTimeConstantEvaluator not implemented
 CTConstTest: Fail # map not implemented
 CallOperatorTest: Fail # Unexpected token 'call'
-CallThroughGetterTest: Fail # Internal Error: Cannot find value
 CanonicalConstTest: Fail # map not implemented
 CharEscapeTest: Fail # Unhandled non-BMP character: U+10000
 ConstInitTest: Fail # CompileTimeConstantHandler with arguments not implemented
@@ -39,7 +38,6 @@
 Factory3Test: Fail # Handling of compile-time constants.
 FinalSyntaxTest/none: Fail # Incorrect compile-time constant handling.
 ForTest: Fail # SsaBuilder for loop without condition not implemented
-FunctionSyntaxTest: Fail # Internal Error: Cannot find value
 FunctionTypeAlias2Test: Fail # cannot resolve type f1
 FunctionTypeAlias3Test: Fail # cannot resolve type F
 FunctionTypeAlias4Test: Fail # cannot resolve type F
@@ -111,7 +109,6 @@
 ListLiteral3Test: Fail # Expect.equals(expected: <true>, actual: <false>) fails.
 ListLiteral4Test: Fail # Expect.equals(expected: <110111>, actual: <null>) fails.
 ListTest: Fail # TypeError: Object ,,, has no method 'copyFrom$4'
-LocalFunction3Test: Fail # Expect.equals(expected: <Closure>, actual: <Instance of 'Closure'>) fails.
 Private3Test: Fail # Expect.equals(expected: <-1>, actual: <The Ring>) fails.
 PrivateTest: Fail # Expect.equals(expected: <99>, actual: <499>) fails.
 ToStringAsFixedTest: Fail # Expect.equals(expected: <0.0000006>, actual: <0.0000010>) fails.