gallery: fix randsvd by adding missing dependency qmult(). * scripts/special-matrix/gallery.m (randsvd) was copied from the Test Matrix toolbox by Nicholas J. Higham. It made use of qmult() which was also part of that toolbox but was left behind. This qmult() implementation is also recovered from the Test Matrix toolbox. Note that Octave itself used to have qmult() which is part of the legacy quaternion package (now also removed from the new quaternion package). See cset 21904fe299c8 for when qmult() was removed from Octave. Also fix the default value for KL and KU so that a 2 element vector can be used as N.

7f19e7f2afa2b1476983003f9cd6df2f5b2a4b08 gnulib-hg