While reading a single byte or uint16 from an input stream is fairly
simple and uncontroversial, the code to read a line or read up to any of
a set of stop characters is not so trivial. People may be using
`GDataInputStream` to parse untrusted input like this, so we should
probably test that it’s robust against a variety of input conditions.
Signed-off-by: Philip Withnall <pwithnall@gnome.org>