[O] Bug: named columns in tables not working if name contains "_"

[András Major]

Hi,

Yet another one I just stumbled across: if I create a table and use
"!" in the first column to assign names to the columns, I can only
reference those columns by name in #+TBLFM: if the names don't contain
a "_" character.  This isn't mentioned in the docs and shouldn't be
so, IMHO.  I haven't checked for other common characters that are
prohibited, but the "_" bites me quite a bit.

  András