Add test for type constraints with type parameters

For #108.

Apparently, higher *order* types and higher *rank* types are different
things, which we’re both going to support as part of #108, so I invented
the name “higher types” for the test file :)

source/test/ceylon/formatter/testSamples.ceylon

@@ -539,3 +539,8 @@ test
 shared void testDestructure() {
     testFile("destructure");
 }
+
+test
+shared void testHigherTypes() {
+    testFile("higherTypes");
+}

test-samples/higherTypes.ceylon

@@ -0,0 +1,4 @@
+interface SecondOrder<Box>
+        given Box<Value> {
+    shared formal Box<Float> createBox(Float float);
+}