This fixes a bug where it was assumed that 'is_suffix' when CRLF
handling was enabled mean that '\r\n' was present. But that's not the
case, and it is intentional that 'is_suffix' only looks for '\n'. (Which
is why #1803 wasn't taken, which tries to fix this by changing
'is_suffix'.)
Fixes#1765, Closes#1803