libcaps thread testing code committed

[Matthew Dillon]

:I dont think this will work. Anything before the pIII did not have SSE,
:so PPro, PII, old Xeons are now useless?  Also, even the pIII only had
:SSE, not SSE2, so there is no way to do double precision floating point
:with just SSE.  Any Athlon before they went to XP I believe does not
:have SSE, and I think there might also be no SSE2 in AMD Chips except
:Athlon64 and maybe Barton.  I dont think this many CPU families can be
:dropped.  They will have to be supported though.
:
:-Craig

    Right.  We can't drop support for the original NPX floating point.  
    However, that doesn't mean we have to save/restore the npx fp context
    for programs that do not use it at all.  This would be an easy
    optimization.  What we can't do is use OS support to optimize mixed
    threaded environments where some threads use NPX and others use SSE*.

    In mixed environments the threading system either has to be told which
    threads are using what, or it has to save sufficient context to cover
    all FP subsystems in use (npx, sse, etc).

						-Matt