Add x86_64 code generation support

Utilizes r0..r7 in register allocator, implements spill/unsill
core regs as well as operations with stack pointer.

Change-Id: I973d5a1acb9aa735f6832df3d440185d9e896c67
Signed-off-by: Dmitry Petrochenko <dmitry.petrochenko@intel.com>
11 files changed