When we xo_open_container() the XML output code generates a tag. There
are some constraints to the tag name which the code does not take into
account. Namely, the tag may contain numbers, but cannot start with a
number.
That constraint is not respected by the calling code, at least in
procstat --libxo xml -ta and potentially in other callers as well.
Tag names are allowed to start with underscores though, so if the tag
starts with something that's not a letter (or underscore) we prefix an
underscore. This changes only the XML output, but presents no risk of
changing schemas people rely on, because the output was previously not
valid XML.
Reported By: Mark Saad