Make OPENSSL_cpu_caps() machine independent.

Make OPENSSL_cpu_caps() machine independent.

OPENSSL_cpu_caps() is currently machine dependent and exposes CPUID data
on amd64 and i386. However, what it is really used for is to indicate
whether specific algorithms are accelerated on the given hardware. Change
OPENSSL_cpu_caps() so that it returns a machine indepent value, which
decouples it from amd64/i386 and will allow it to be used appropriately
on other platforms in the future.

ok tb@