Add missing cast.

src/platform-linux.cc

Index: src/platform-linux.cc
===================================================================
--- src/platform-linux.cc	(revision 7048)
+++ src/platform-linux.cc	(working copy)
@@ -584,7 +584,7 @@
   // This is also initialized by the first argument to pthread_create() but we
   // don't know which thread will run first (the original thread or the new
   // one) so we initialize it here too.
-  prctl(PR_SET_NAME, thread->name(), 0, 0, 0);
+  prctl(PR_SET_NAME, reinterpret_cast<unsigned long>(thread->name()), 0, 0, 0);
   thread->thread_handle_data()->thread_ = pthread_self();
   ASSERT(thread->IsValid());
   thread->Run();