Some strange icons in Table of Contents

[gagachang]

There are some strange icons in Table of Contents:

[pdonahue-ventana]

Depending on what I use to view the file, I sometimes see the same thing. In particular, Acrobat Reader on Windows shows those boxes. Since that's probably the most popular PDF viewer, this is something that should be addressed.

The python script generates this type of thing:

[[dm-dmcontrol]]
==== Debug Module Control (((dmcontrol)), at 0x10)

It looks like there's a TODO on the code that generates this: https://github.com/riscv/riscv-debug-spec/blob/main/registers.py#L979

I know very little about asciidoc but maybe the double parentheses should be backticks. We use those for registers elsewhere, but I'm not sure if that works in section titles like this.