Add the very basics of Intel 32-bit instruction encodings.

Tabulate the Intel opcode representations and implement an OP() function
which computes the encoding bits.

Implement the single-byte opcode with a reg-reg ModR/M byte.

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

@@ -0,0 +1,10 @@
+"""
+Intel Encodings.
+"""
+from __future__ import absolute_import
+from base import instructions as base
+from .defs import I32
+from .recipes import Op1rr
+from .recipes import OP
+
+I32.enc(base.iadd.i32, Op1rr, OP(0x01))