[RFC] Implement pthread_getthreadid_np(3) and pthread_getunique_np(3)

[Jung-uk Kim]

Our pthread_t is not an integral type and it causes a lot of trouble 
porting some software, which relies on Linux's gettid() or similar 
syscalls:

http://www.kernel.org/doc/man-pages/online/pages/man2/gettid.2.html

For example:

http://docs.freebsd.org/cgi/mid.cgi?201102032111.13479.jkim

To solve this problem, I implemented two functions:

http://people.freebsd.org/~jkim/thr_tid.diff

Basically, they are AIX's pthread_getthreadid_np(3) and 
pthread_getunique_np(3) look-alikes:

http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/apis/users_22.htm
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/apis/users_23.htm

Please let me know what you think.

Thanks!

Jung-uk Kim