Several improvements; see description

• Improved Xd (spdiags): now it allows vector input with two outputs (Matlab and Octave don't)
• u in stable mode now produces up to three outputs
• u with numeric cell array now allows sorted and stable modes
• Corrected a bug in the pad values used by e (reshape). Thanks, @suever! Also, this function with character input now pads with character 0
• Octave compatibility. Ym (mean) and ' Zs(std`) now allow char input
• Some functions now allow a number instead of a string input flag. Specifically (more may be added in the future): unique, intersect, union, setdiff, setxor, conv, regexp, regexprep, sum, mean, strsplit, interp1, pdist2, accumarray, gallery, padarray.
• Zn now also computes the determinant of a square matrix