Implement changes for the new mednafen 1.21.0-UNSTABLE

[Asnivor]

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[Asnivor]

Items from 1.21.0-UNSTABLE changelog that specifically need addressing in MedLaunch:

• Removed the "overlay" video driver

• Changed the default value of setting "video.driver" from "opengl" to "default", removed the old "0" and "1" backwards-compatibility value aliases, renamed the "sdl" driver to "softfb"(without backwards-compat aliases), and made it so the setting's value will be reset to "default" after automatically importing settings from "mednafen-09x.cfg"

• Added setting "video.fs.display"

• Added settings "fps.autoenable", "fps.position", "fps.scale", "fps.font", "fps.textcolor", and "fps.bgcolor"

• On Windows, Mednafen will now output text to a console if it's started from a console(e.g. cmd.exe or Cygwin), and if not, write to stdout.txt and stderr.txt like before

• On Windows, error messages during startup will now be displayed in a popup message box

• Configuration file is now named "mednafen.cfg" again, instead of "mednafen-09x.cfg"; if "mednafen.cfg" doesn't exist or is for an old version(earlier than 0.9.0) of Mednafen, the settings will be loaded from "mednafen-09x.cfg" on startup, but still saved to "mednafen.cfg" on exit.

• Reworked the input mapping setting format to be more human-readable(and editable). Details are in the documentation, in the "Advanced Usage" section. Old input mappings will be translated internally, except for keyboard mappings, due to incompatibilities between how SDL 1.2 and 2 handle keyboards.

• Added support for mapping joystick axes and buttons, mouse buttons, and keyboard keys to emulated mouse device relative motion for testing purposes(via manually editing the configuration file, as the in-emulator configuration process currently won't create such mappings).

• Added support for digital button input mappings that mix AND, ANDNOT, and OR-style operations together(previously it was either just AND or OR); refer to the documentation for more details. Note that the in-emulator configuration process won't create complex mappings that mix different boolean operations, but you can map combinations using simpler logic in-emulator, and then edit the configuration file to adjust the boolean operations used.

(I will be ticking these off as I go BEFORE the changes are pushed to dev. They will only be available once a new dev version is built and released)