Created by: fhahn
This patch adds encoding & decoding support for most arithmetic FP Neon instructions. The structure of the generated macros and tests follows the style of #2896.
codec.txt contains comments if not all encodings of an instruction are supported yet. Also missing are the Arm v8.3-a FCADD and FCMLA instructions, because their rotation arguments require a bit of special handling to get nice macros.
Issue #2626