Clarify the end-steps of WaitForIncoming().

This is C.  The results of comparison operators and "boolean" binary operators are 0 or 1, not false or true, although of course bool is so defined as to make the natural usage valid.  If you really want, we can [while not bored yet, do] bung `(...)` round the whole of the conditional just given and append the utterly fatuous `? 1 : 0` [done, and repeat a few times for the sake of parody] but there is no value to doing so.