first patch for process-shared semaphore

[David Xu]

This is my first attempt to make process-shared mutex work, this means
you can mmap(MAP_SHARED) a memory area, and put semaphore there,
or you can sem_open a named semaphore, and just use it between
processes, the named semaphore uses file system and mmap(), directory 
/tmp/.semaphore is used as IPC directory, any named semaphore
locates in the directory. old semaphore implementation still exists
to make it binary compatible, it uses symbol version.

http://people.freebsd.org/~davidxu/patch/shared_semaphore_1.patch


David Xu