Add/Update tests for Yul function definition

test/libsolidity/syntaxTests/inlineAssembly/function_definition.sol

@@ -0,0 +1,8 @@
+contract C {
+  function f() pure public {
+    assembly {
+      function f (a, b  , c ) ->    y,x,z {
+      }
+    }
+  }
+}

test/libsolidity/syntaxTests/inlineAssembly/function_definition_whitespace.sol

@@ -0,0 +1,8 @@
+contract C {
+  function f() pure public {
+    assembly {
+      function f (a, b  , c ) -     >    y,x,z {
+      }
+    }
+  }
+}