New SCHED_SMP diff.

[Jeff Roberson]

I fixed a major bug in SCHED_SMP that impacted some users causing bad 
performance and invalid load counts.  Attilio also added support for i386 
based machines.  I have tested on UP which works although INVARIANTS and 
WITNESS don't work properly on UP kernels.  Single processor SMP kernels 
work fine.

This diff also includes another patch that I intend to commit to current 
which significantly improved write performance for mysql by removing 
all use of Giant in fcntl().

Please report any stability or performance problems with this patch.  The 
more positive reports I get the more likely it will go into 7.0.

Thanks,
Jeff