Add test for E0628 (too many generator parameters)

src/test/ui/generator/too-many-parameters.rs

@@ -0,0 +1,7 @@
+#![feature(generators)]
+
+fn main() {
+    |(), ()| {  //~ error: too many parameters for generator
+        yield;
+    };
+}

src/test/ui/generator/too-many-parameters.stderr

@@ -0,0 +1,8 @@
+error[E0628]: too many parameters for generator (expected 0 or 1 parameters)
+  --> $DIR/too-many-parameters.rs:4:5
+   |
+LL |     |(), ()| {
+   |     ^^^^^^^^
+
+error: aborting due to previous error
+