- Add IPC_OS_FREEBSD_ platform detection macro
- Enable FreeBSD to use POSIX pthread implementation (shared with QNX)
- Update all conditional compilation directives to include FreeBSD
- Update README to reflect FreeBSD platform support
FreeBSD uses the existing POSIX implementation which supports:
- Process-shared mutexes (PTHREAD_PROCESS_SHARED)
- Robust mutexes (PTHREAD_MUTEX_ROBUST)
- Timed lock operations
- POSIX shared memory
This is a minimal change that reuses the mature POSIX implementation
already proven by QNX platform support.
