Accept only takes one argument, needs to detect error

Lucie got bit by a copy/paste error where an accept clause in a sender had a space in it. It caused warnings not to get translated until we caught it.

accept clauses only take one argument. It would be good if sundew indicated (error message? fail to start up) when there is a clear syntax error in an accept, or a reject.

was: https://sourceforge.net/p/metpx/bugs/29/

No files or tests are named. Locate the parser or startup entry point handling accept and reject clauses, then reproduce the copy/paste case where an accept clause contains a space. Done means a clear syntax error is reported or startup fails for invalid accept or reject clauses, with valid clauses still accepted.

Written by the indexing model from the issue text.