Typo
Missing "math" in cathode setting for subscripts
Missing arg when creating message
Fixing message means fixing test file
Some code now moved to the new sources removed from the v2 file
Variable is now internal, so mark as such
Add "number/input/..." options

A couple of options from v2 are removed here. The idea of protecting
tokens I think is actually not needed if the expansion step is
improved (LaTeX2e so \protected@edef is required). The option for
symbols is also going: the idea here is that if people really want to do
non-standard input it should either not be parsed or be treated as a
'number' (at the risk of the user).
Stick with "number/input-..."

It's not clear that these should be a 'full' subdivision as there is
no obvious match for output or similar.
Function is internal not auxiliary
Missing argument
Improve comment
A variable to hold numeric input