Firmware v20230820

• Added SpecDrum support (Covox variation on #DF port);
• Added option to remap gamepad button A as UP;
• Increased AY volume;
• Implemented fast 48 Basic boot when "Auto CPU freq" option is enabled;
• Slightly improved 128 int timings;
• Fixed 128 Basic crash when DivMMC is enabled;
• Fixed esxDOS TAP file loading in +3e mode;
• Fixed ULA+ IO contention for classic timings (HAM256.TAP has been affected)
• Fixed Magic button handling when DivIDE addon is installed;
• Attribute port is now accessible only via #FF address in classic timings. This is necessary to prevent a bus conflict when reading ports from addons. Pentagon mode hasn't been affected as it's already used only #FF port in previous versions.