Document SMP detection code.

doc/TODO

 TODO list for PostgreSQL
 ========================
-Last updated:		Tue Jan 22 16:54:39 EST 2002
+Last updated:		Tue Jan 22 17:14:43 EST 2002
 
 Current maintainer:	Bruce Momjian (pgman@candle.pha.pa.us)
 
@@ -387,6 +387,7 @@ LOCKING
 
 * Make locking of shared data structures more fine-grained
 * Add code to detect an SMP machine and handle spinlocks accordingly
+  http://www1.distributed.net/source, in client/common/cpucheck.cpp
 * Research use of sched_yield() for spinlock acquisition failure
 * -Improve spinlock code [performance] (Tom)