Rename from_utf8 to from_bytes again
auto merge of #9500 : fhahn/rust/rename-str_from_bytes-fix, r=alexcrichton

As @Dretch pointed out [here](https://github.com/fhahn/rust/commit/de39874801761197bf10bf8d04bde1aa2bd82e15#L2L526) , from_bytes was accidentally renamed to from_utf8.