`(c-u* U1 U2) → list`syntaxUnary multiplication. Yields a list containing the contents of the first list, repeated once for every item in the second list.

Based on

`c-mul`from the original implementation, except the symbol 'u has no special significance, and result is made from duplicating the first list.(ck () (c-quote (c-u* '(a b) '(c d e)))) ;; ==> '(a b a b a b)