QFS_NextFilename was renamed to QFS_NextFile to reflect the fact it now
returns a QFile pointer for the newly created file (as well as the
name). This necessitated updating WritePNG to take a file pointer
instead of a file name, with the advantage that WritePNGqfs is no longer
necessary and callers have much more control over the creation of the
file.
This makes QFS_NextFile much more secure against file system race
conditions and attacks (at least in theory). If nothing else, it will
make it more robust in a multi-threaded environment.
a29836cc2c