Fix build failure on clang with boost 1.41
Fix build failure on clang with boost 1.41

boost/thread.hpp appears to include some part of boost which
has bad code that clang 3.2 barfs on. We just need thread/thread.hpp
in this case.

cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,InspurUSA/kudu,cloudera/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,andrwng/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,andrwng/kudu,EvilMcJerkface/kudu,cloudera/kudu,helifu/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,andrwng/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,cloudera/kudu,helifu/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,andrwng/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,andrwng/kudu,helifu/kudu,cloudera/kudu,andrwng/kudu,cloudera/kudu,cloudera/kudu,InspurUSA/kudu