Generate register bank descriptions.

Use the information in the ISA's registers.py files to generate a
RegInfo Rust data structure.

lib/cretonne/meta/isa/intel/__init__.py

@@ -17,6 +17,7 @@ is no x87 floating point support.
 
 from __future__ import absolute_import
 from . import defs
+from . import registers  # noqa
 
 # Re-export the primary target ISA definition.
 ISA = defs.ISA.finish()