Additional facilities for printing numbers

prnum(NUM, INT_PLACES, FRAC_PLACES)
    This takes any non-complex number NUM and prints it in the form
        <pre>.<post>
    INT_PLACES is an integer specifying the number of character
    positions that <pre> should occupy, including leading spaces, and
    minus sign, if NUM is negative. FRAC_PLACES specifies the number of
    positions the <post> part should occupy, excluding the ".", and
    including trailing zeros if necessary. E.g.

    pr("|"); prnum(-3.52, 4, 5);pr("|");
    |  -3.5200|

radix_apply(ITEM_1, ITEM_2..., ITEM_N, P, RADIX)
    Runs the procedure P, which should take N arguments, ITEM_1 to
    ITEM_N, in an environment in which pop_pr_radix has the integer
    value RADIX. So any printing done by P uses that value of
    pop_pr_radix. E.g.

    radix_apply(45,5,5,prnum,16);
       2D.0000

    printf, nprintf, pr_field, format_print