Drop some special-casing for ASCII during UTF-8 encoding
Drop some special-casing for ASCII during UTF-8 encoding

I somehow forgot that we allocate the initial ByteString to contain
the same number of bytes as the Text contains code units. This means
that we never need to ensure that the ByteString is big enough, nor
(with this observation) does a special-cased ASCII-only loop help
performance.

23Skidoo/text,alexliew/text,aloiscochard/text,aloiscochard/text,spencerjanssen/text,bos/text,aloiscochard/text,beni55/text,spencerjanssen/text,text-utf8/text,bos/text,spencerjanssen/text,ekmett/text,ekmett/text,hvr/text,hvr/text,alexliew/text,23Skidoo/text,text-utf8/text,alexliew/text,alexliew/text,ekmett/text,bos/text,hvr/text,text-utf8/text,23Skidoo/text,23Skidoo/text,ekmett/text,text-utf8/text,bgamari/text,hvr/text,bos/text,spencerjanssen/text,beni55/text,beni55/text,bgamari/text,bgamari/text,aloiscochard/text,beni55/text,bgamari/text