Update ax_boost* macros, add ax_boost_thread.m4

Summary:
Fixes

checking whether the Boost::Thread library is available... yes
configure: error: Could not find a version of the library!

Test Plan: OSS Build

Reviewed By: meyering@fb.com

Subscribers: alandau, jhj, kma, lesha

FB internal diff: D1428785

Blame Revision: D1420185