Add more syntax tests for enums and interfaces/libraries

test/libsolidity/syntaxTests/parsing/enum_from_interface.sol

@@ -0,0 +1,9 @@
+interface I {
+    enum Direction { Left, Right }
+}
+
+contract D {
+    function f() public pure returns (I.Direction) {
+      return I.Direction.Left;
+    }
+}

test/libsolidity/syntaxTests/parsing/enum_from_interface_in_library.sol

@@ -0,0 +1,12 @@
+interface I {
+    enum Direction { Left, Right }
+}
+
+library L {
+    function f() public pure returns (I.Direction) {
+      return I.Direction.Left;
+    }
+    function g() internal pure returns (I.Direction) {
+      return I.Direction.Left;
+    }
+}

test/libsolidity/syntaxTests/parsing/enum_from_library.sol

@@ -0,0 +1,9 @@
+library L {
+    enum Direction { Left, Right }
+}
+
+contract D {
+    function f() public pure returns (L.Direction) {
+      return L.Direction.Left;
+    }
+}

test/libsolidity/syntaxTests/parsing/enum_inheritance_contract.sol

@@ -0,0 +1,9 @@
+contract C {
+    enum Direction { Left, Right }
+}
+
+contract D is C {
+    function f() public pure returns (Direction) {
+      return Direction.Left;
+    }
+}

test/libsolidity/syntaxTests/parsing/enum_inheritance_interface.sol

@@ -0,0 +1,9 @@
+interface I {
+    enum Direction { Left, Right }
+}
+
+contract D is I {
+    function f() public pure returns (Direction) {
+      return Direction.Left;
+    }
+}