Fixed typo.
Bugfix: command line arguments print error

The command line arguments weren't being printed when passed to
argerror. For instance, a user might type something like the following:

mcell -seed not_a_number my_mdl.mdl

In this case, MCell should have printed the following error message:

Random seed must be an integer: not_a_number

The problem was that one variadic function (argerror) was calling
another (mcell_error_raw) before calling va_end causing MCell to either
segfault or print gibberish.

A couple other small changes were made:

- The unused vol arguments were removed.
- References to short options in error messages were removed.
Small cleanup of previous commit.