Merge pull request #12545 from ethereum/yulGrammarFluke

Allow builtins in yul identifier paths in antlr grammar.

test/libsolidity/syntaxTests/inlineAssembly/assignment_to_function_pointer.sol

@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        function() external g;
+        assembly {
+            g.address := 0x42
+            g.selector := 0x23
+        }
+    }
+}