Beim Lesen von PSP (C)ISOs kam es zu einer Division durch Null, die zum Absturz führte. Dieser und weitere Fehler wurden behoben.

Bug fixes:
* Fix a division by zero when reading PSP CISO/CSO images.
* * This bug was reported by @NotaInutilis in issue #286.
* Fix a crash in the BC7 and PVRTC image decoders if the image dimensions were not a multiple of the tile size.
* rp-download: Allow clone3(), which is needed on systems that have by glibc-2.34.

Other changes:
* GTK+ frontends now use libgsound if available.
* Experimental support for GTK4 has been added. It's not available by default (configuration is commented out in CMake), since none of the major file browsers support GTK4 yet.