Adding a function to stdlib to set the min stack size, for programs

that absolutely will not succeed with a large default stack. This
should be removed once we have stack grown working.

Also updated word-count to succeed under the new test framework.

src/rt/rust_builtin.cpp

@@ -856,6 +856,13 @@ clone_chan(rust_task *task, rust_chan *chan) {
     return chan->clone(task);
 }
 
+// defined in rust_task.cpp
+extern size_t g_min_stack_size;
+extern "C" CDECL void
+set_min_stack(rust_task *task, uintptr_t stack_size) {
+    g_min_stack_size = stack_size;
+}
+
 //
 // Local Variables:
 // mode: C++