Vectorized hold

Vectorized version of hold function.

VHOLD(multiax, onoff) set hold state of multiple axes.
VHOLD(multiax, onoff) is a vectorized version of function hold.
It sets the states of multiple axes objects with handles in matrix
multiax, to the states provided in onoff. Argument onoff can be a
single string, 'on' or 'off', setting all the axes to that hold state,
or a cell matrix of strings 'on', 'off', setting individual axes to
(possibly) different states. Note that in the second case, matrix
multiax and cell matrix onoff should have the same size, i.e.,
size(multiax) should equal size(onoff), if onoff is a cell matrix.

usage
VHOLD(multiax, onoff)

input
multiax = matrix of handles to axes objects
= [ax11, ax12, ..., ax1m;
ax21, ax22, ..., ax2m;
: : : :
axn1, axn2, ..., axnm];
onoff = hold states for axes objects with handles in array multiax
= 'on' (to set all axes objects hold states to 'on') |
= 'off' (to set all axes objects hold states to 'off') |
= {'on', 'off', 'off', ..., } (to set individual hold states)