[VCS] Stella 3.7.3

Task Force (Froggo, 1987)

Stella 3.7.2 to 3.7.3: (October 26, 2012)

• because of TIA/RIOT changes, the state file format has changed again, and old state files will not work with this release.
• Improved handling of 'illegal' VSYNC signals, which sometimes created 'short' frames that caused massive flickering. Also improved related behaviour when VSYNC isn't used at all.
• Improved sound generation with ROMs that have irregular scanline counts. This fixes many demo ROMs as well as Quadrun, where previously there would be 'gaps' in the sound output.
• Improved emulation of RIOT chip, in particular the behaviour of reading from TIMINT. Also, D6 of the Interrupt Flag register is now properly set on active transition of the PA7 pin.
• Fixed bug in DPC+ bankswitch scheme; the music in "Stay Frosty 2" wasn't playing correctly.
• The ROM properties database now uses 'Auto' instead of 'Auto-select' everywhere. This makes for less typing when running from the commandline.
• Updated included PNG library to latest stable version.