x86_64: Rebase on top of "64-bit temp register support"

Added the 64-bit core/temp register definition, fixed RegisterPool
creation for x86_64 so that 64-bit core/temps are NOT used for now.
The long arithmetic still operates with register pair on x86_64 and
it is a subject for change in a separate patch.

Change-Id: I2be06d5aefaf80141983bc9d8ed8a2ee24c2b21b
Signed-off-by: Dmitry Petrochenko <dmitry.petrochenko@intel.com>