Changes to the SystemZ Target

* Support for the arch13 architecture has been added. When using the

``-march=arch13`` option, the compiler will generate code making use of

new instructions introduced with the vector enhancement facility 2

and the miscellaneous instruction extension facility 2.

The ``-mtune=arch13`` option enables arch13 specific instruction

scheduling and tuning without making use of new instructions.

* Builtins for the new vector instructions have been added and can be

enabled using the ``-mzvector`` option. Support for these builtins

is indicated by the compiler predefining the ``__VEC__`` macro to

the value ``10303``.

* The compiler now supports and automatically generates alignment hints

on vector load and store instructions.

* Various code-gen improvements, in particular related to improved

instruction selection and register allocation.