fuzzing: Add fuzz tests for GDataInputStream’s complex read methods

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