Allow multiple arguments to na_if

[nalimilan]

It's quite frequent to have to recode several distinct values to NA. So far the shortest solution I could find to do that is e.g. na_if(na_if(vec, 88), 99). if_else(vec %in% c(88, 99), NA_real_, vec) or case_match(vec, c(88, 99) ~ NA, .default=vec) are also possible but relatively verbose. Could it be allowed to pass multiple arguments to na_if so that one could write na_if(vec, 88, 99) instead?

[hadley]

Duplicate of #7651