When saving a user-defined formula by specifying its ~z-~ key, or the
~M-x~ command name, its compositions are not saved correctly. The
attached patch fixes this behavior.

--- notes on the code change ---

~func~ is the calcFunc- symbol representing the formula.
~cmd~ is either the calc- symbol representing the command, or, if we
are saving just the formula, the calcFunc- symbol.

We always want to associate the composition forms to the calcFunc-
version. Observe for example that two lines below, this is the symbol
that we pull them from to save.