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>

fuzzing/meson.build

@@ -19,6 +19,9 @@
 fuzz_targets = [
   'fuzz_bookmark',
   'fuzz_canonicalize_filename',
+  'fuzz_data_input_stream_read_line',
+  'fuzz_data_input_stream_read_line_utf8',
+  'fuzz_data_input_stream_read_upto',
   'fuzz_date_parse',
   'fuzz_date_time_new_from_iso8601',
   'fuzz_dbus_message',