vector instructions support

Vector instructions are currently unsupported but they are used, particularly in standard libraries.

One good place to start would be A32 encodings, prioritizing `vpush, vpop, vldr, vstr, vmov`.

The bigger challenge is dealing with 64-bit registers (`d0 - d31`) and their alternate views (32-bit regs `s0 - s31` and 128-bit regs `q0 - q15`).
