A64: Introduce 'branch types' that extend the architectural conditions.

The branch types include 'always' and 'never', and types like reg_zero (CBZ) and
reg_bit_clear (TBZ).
This will be used by incoming improvements to the code generated for
deoptimization exit points.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/170783002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19497 ce2b1a6d-e550-0410-aec6-3dcde31c8c00