[kernel] Support for top-level generic functions.

pkg/kernel/testcases/closures/catch.dart.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 static method main() → dynamic {
   dynamic c;
   try {
     throw "Fisk";
   }
   on core::String catch(dynamic #t1, dynamic #t2) {
-    final Vector #context = MakeVector(3);
-    #context[1] = #t1;
-    #context[2] = #t2;
+    final Vector #context = MakeVector(4);
+    #context[2] = #t1;
+    #context[3] = #t2;
     c = MakeClosure<() → dynamic>(self::closure#main#function, #context);
   }
   c.call();
   core::print("TEST PASSED");
 }
 static method closure#main#function(Vector #contextParameter) → dynamic {
-  core::print(#contextParameter[1]);
-  if(!(#contextParameter[2]).==(null))
-    core::print(#contextParameter[2]);
+  core::print(#contextParameter[2]);
+  if(!(#contextParameter[3]).==(null))
+    core::print(#contextParameter[3]);
 }