Add type inference for while and do loops.

pkg/front_end/testcases/kompile.status

Index: pkg/front_end/testcases/kompile.status
diff --git a/pkg/front_end/testcases/kompile.status b/pkg/front_end/testcases/kompile.status
index 7e959679b5da9336c3b891f1b510c40be335985d..3b79705a21a92e488e1f53ffb0c2b9d022e8aac2 100644
--- a/pkg/front_end/testcases/kompile.status
+++ b/pkg/front_end/testcases/kompile.status
@@ -391,6 +391,7 @@ inference/unsafe_block_closure_inference_method_call_no_type_param: Crash
 inference/void_return_type_subtypes_dynamic: Crash
 inference_new/dependency_only_if_generic_method: Crash
 inference_new/dependency_only_if_overloaded: Crash
+inference_new/do_loop: VerificationError
 inference_new/downwards_inference_inside_top_level: Crash
 inference_new/downwards_inference_inside_top_level_2: Crash
 inference_new/field_inference_circularity: Crash
@@ -410,6 +411,7 @@ inference_new/strongly_connected_component: Crash
 inference_new/unsafe_block_closure_inference_function_call_explicit_dynamic_param_via_expr2: Crash
 inference_new/unsafe_block_closure_inference_function_call_explicit_type_param_via_expr2: Crash
 inference_new/void_return_type_subtypes_dynamic: Crash
+inference_new/while_loop: VerificationError
 
 rasta/abstract_constructor: Fail
 rasta/bad_constructor_redirection: Crash