Notes:
Changes in version 1.1.0
------------------------

* implemented 1551 drive emulation
* added floppy drive LED display to the GUI (1541 is red, 1551 is
green, and 1581 is yellow)
* the debugger now allows for debugging floppy drives; the drives are
also mapped to the physical address range $180000-$1BFFFF
* fixed 1541 disk change detection
* keyboard map can be configured with the GUI
* external game devices like joysticks and gamepads are supported, and
can be assigned in the keyboard map like normal keys
* the ´step over´ button in the debugger now also skips branch
instructions
* invalid opcodes that normally jam the CPU can be used as breakpoints
(with the priority assumed to be 3) that open the debugger, and the
execution of the program can continue as if there was a NOP
instruction
* added new command line options for loading disk image, snapshot, and
demo files on start-up; on Windows, D64 and D81 files are also
optionally associated with the emulator
* it is now possible to use WAV, AIFF, and other sound file formats as
tape images; these files can be read and written, however, new files
are created in plus4emu format
* blank video output is generated when the TED is disabled by setting
bit 5 of $FF07
* reduced horizontal texture resolution to 384 in OpenGL mode when the
quality is set to 0, for improved performance
* minor GUI improvements and fixes