The SSE spec ends a line with CRLF, LF or CR, but SSEClient split only
on LF, so a stream that uses CR alone never produced an event. The LF
of a CRLF is skipped even when it arrives in a later chunk than its CR.
Search for a line ending only in the newly received data. What is left
in the buffer has none, and scanning it again for every chunk made a
long line quadratic.