Dynamically allocated locks

[Andrew Doran <ad%netbsd.org@localhost>]

Hi,

This patch allows for dynamically allocated locks.

http://www.netbsd.org/~ad/lockobj.diff

Each lock gets its own cache line, which can reduce cache coherency costs
when the lock is very active. The locks are reference counted so can be
shared between objects. That could be used for the two ends of a Unix socket
connection, or to share a lock between clone()d processes in order to
protect common state like signal actions, etc.

Any objections?

Thanks,
Andrew