Added module for querying propetery tags from VCOS via mailbox
Changed uart registers from 8bit/16bit to 32bit wide

I had originally set these register definitions to the "correct" size
hoping to catch possible mistakes via c's type system.

Unfortually, c's type system isn't strict enough and will automaitcally
cast between intergers (and floats) of diffrent sizes, which caused a hard
to track down bug when I copy/pasted the register definition type from uart.c
to another device which did have 32bit wide registers and c helpfully
trunkcated my reads/writes for me.

Also, ARM does much better with 32bit read/writes so I'm changing these back.