[spec review] DWARF for the Arm 64-bit Architecture

[stuij]

It has been a while since we did a sanity check on the individual ABI documents. Lets do a review pass over them and check for things like:

• internal consistency
• outdated sections
• plain wrong sections
• proper rendering in HTML and PDF
• adherence to ABI style
• dates/licensing in order

Small things we can fix as part of this issue. For bigger things, create a new issue.