Elna

A new attribute #varargs should be introduced. Only valid positions for this attribute are procedure declaration and type: #varargs proc f(x: Int) extern or var x: #varargs proc(x: Int).

• In procedure declarations `#varargs' is supported only on extern procedures.
• Type checker should be extended to check for this attribute and adjust argument checking. Also assignment checking should be modified to disallow assigning variadic to non-variadic procedures or vice versa.
• Arguments passed through the variadic part need the C default promotions, e.g. Word8 and Bool widened to int, Single to Double.