#520 make_array arrays not well integrated

[Stavros Macrakis]

make_array arrays are useful but ugly.

They don't print properly:

ar: make_array(any,3)$
ar[1]: sin(x)$
ar => #(NIL ((%SIN SIMP) $x) NIL)

and even worse:

string(ar) =>
?\#\(NIL\ \(\(\%SIN\ SIMP\)\ \$x\)\ NIL\)

There is no way to write a constant array, so you can't
save it in Maxima form.

It's a pity that the function name "array" is taken... but
we could define the external form of an array to be
something like:

array_constant( <<type and maybe size>>,
[ ...contents... ] )

e.g.

array_constant(any,[2,3,4])

is the same as

block([arr],arr:make_array(any,3),
for i:0 thru 2 do arr[i]:[2,3,4][i])

etc.