Free GdkIOPipe struct when freeing it Don't just free all its members. Fixes #5110
Replace leftover gtk-doc syntax (#Type) with backquotes.
The variable is never read again.
This requires implementing a "pipe" so we can have 2 streams running: contentprovider => serializer => outputstream inputstream => deserializer => reader And the pipe shoves the data from the outputstream into the inputstream.
