1.Macro optimizing KSE_LOCK_ACQUIRE and THR_LOCK_ACQUIRE to use static fall
through branch predict as suggested in INTEL IA32 optimization guide.

2.Allocate siginfo arrary separately to avoid pthread to be allocated at
2K boundary, which hits L1 address alias problem and causes context
switch to be slow down.

3.Simplify context switch code by removing redundant code, code size is
reduced, so it is expected to run faster.

Reviewed by: deischen
Approved by: re (scottl)