illumos gate

POSIX has gone ahead and added a whole new suite of functions that add support for using a specific clockid_t when phrasing an absolute timeout with the mutex, condition variable, and rwlock functions. These can be found here. While normally we want to avoid adding support for these before the specs come out, it appears that libstdc++ and co. are already on their way to use this as these features have been added into glibc and Android's libc. We should evaluate adding support for a chunk of these; however, making sure not to implement anything that hasn't already been implemented by glibc prior to the standards release. Because glibc is already in the wild, it makes some sense to go ahead and add support now.