Reorganize the bits for the CPU feature detection

Instead of trying to detect one bit and set another, let's just use the
bits from the x86 CPUID instruction on x86. This makes use of the full
64-bit space now.

Since MSVC doesn't like enums bigger than 32-bit, we have to store the
bit number instead of the actual bit value in the constant. For that
reason, I also renamed the constants, to catch anyone who was using them
directly, instead of through qCpuHasFeature.

Change-Id: Ib306f8f647014b399b87ffff13f1d587692d827a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>