Maps a function on all elements of a matrix. Modifies the matrix
in-place.
The function name must be a program that operates only on the X
register. XEQ IND doesn't appear to work with names of built-in
functions, but most built-in functions can operate directly on the
matrix with similar results.
Because the matrix is modified in-place, if an error occurs at any
point the matrix may be partially modified. It might be good to save a
copy of the original matrix.
This version is somewhat improved over a previous one by using DSE
instead of ISG to loop and by using -> instead of I+ to move the
matrix index.
Inputs:
M: matrix to map over
F: name of program to map
