[boost] [interprocess] patch for AIX

Hello, Currently interprocess doesn't work on AIX for two reasons : - detail/os_thread_functions.hpp uses ::pthread_equal but this fails because pthread_equal is a macro under AIX and it fails because of the :: prefix - in detail/atomic.hpp there is no implementation of PowerPC under AIX so I added one that uses the combination of lwarx and stwcx for each function to implement. I saw that under AIX, the detail/atomic_count.hpp and detail/sp_counted_base.hpp falls back to a pthread implementation, I could submit a patch for a real atomic implementation under AIX but I wonder if there are other places in boost where this should be done ? Thanks, Etienne PIERRE