c variadic calls

compiler/hir/hir.odin

@@ -93,6 +93,7 @@ Expr_Kind :: enum u8 {
 	Unwrap,
 	Orelse,
 	Widen,
+	C_Vararg_Promote,
 	Weaken_Pointer,
 	Negate,
 	Add,
@@ -144,6 +145,7 @@ Function :: struct {
 	implementation:      Implementation,
 	linkage:             Linkage,
 	is_main:             bool,
+	variadic:            bool,
 	params:              []Local_Id,
 	result:              types.Type,
 	locals:              []Local,