ode "Mass" and "Jacobian" options

[Rik]

The ode solver options "Mass" and "Jacobian" can be either a function
handle or a matrix according to odeset().  If it is a matrix, does that
mean a numeric 2-D matrix or just a numeric N-D array?

The input validation for ode15i and ode15s has to be re-done because of a
change in the behavior of str2func, and I'm taking the opportunity to
improve it.

Thanks,
Rik