Slighly more safety to %MAKE-ARRAY in full call situations.

Most argument errors are caught before attempting memory allocation
e.g. in (MAKE-ARRAY `(1 -2 -3) which has an otherwise valid value
of (reduce #'* dimensions). Mis-shapen :initial-contents are detected
late, but this seems less important.
And incidentally, a full call to (MAKE-ARRAY 1) is 33% less consy.