(ipc_cond_init): Ditto. (struct mq_hdr): Add mqh_uname member to store synchronization object name. (mq_open): Create unique synchronization object name and store in mq_hdr->mqh_uname. Use this name in calls to ipc_mutex_init and ipc_cond_init.
* cygwin.din (mq_close): Export. (mq_getattr): Export. (mq_notify): Export. (mq_open): Export. (mq_receive): Export. (mq_send): Export. (mq_setattr): Export. (mq_timedreceive): Export. (mq_timedsend): Export. (mq_unlink): Export. * posix_ipc.cc: New file implementing the above functions. Move shm_open and shm_unlink from syscalls.cc here. * sysconf.cc (sca): Set value of _SC_MQ_OPEN_MAX to MQ_OPEN_MAX, _SC_MQ_PRIO_MAX to MQ_PRIO_MAX, _SC_MESSAGE_PASSING to _POSIX_MESSAGE_PASSING. * include/limits.h (MQ_OPEN_MAX): Define. (MQ_PRIO_MAX): Define. * include/mqueue.h: New file. * include/cygwin/version.h: Bump API minor number.