Add a machinetype identifier to help us quickly identify
Apple //e (bit 7) and //e enhanced (bit 6).
Use it in conio functions for 80-columns code instead of
relying entirely on the __APPLE2ENH__ target.
Move videomode() to the apple2 target, and have it return
an error if 80-columns hardware is not available - this
is a lie for now, it is considered available on //e enhanced,
which may not be true, and not available on //e, which
may also be not true. An ulterior patch will make that
check correctly.
Adapt the box/line drawing characters so that one can use
MouseText on the apple2 target if it is available, by
defining DYN_DRAW_BOX. No change by default: MouseText is
considered available on apple2enh and not available on
apple2.
In order to avoid undefined behaviour of programs not aware of 80 column mode, the 80 column firmware deliberately doesn't use CH but OURCH. So in order to be fully interoperable, CONIO needs to do the same. This changes introduces that behavior. So far so good.
But the 80 column firmware can also be active in 40 column mode. This scenario is not detectable with reasonable effort. Therefore the behaviour of CONIO in this scenario is _not_ improved. However, this scenario is supposed to be very uncommon - and a recent update to videomode() makes sure to not activate it anymore ourselves.
Notes:
* If a program wants to be 100% sure to not run in 40 column mode with 80 column firmware active it can call videomode(VIDEOMODE_40COL) to explicitly deactivate a potentially active 80 column firmware. However, this always implicitly clears the screen.
* In 40 column mode (contrast to 80 column mode) the 80 column firmware updates CH to reflect OURCH. So as long as CONIO only reads CH, but doesn't update it, everything works as expected. Interestingly this makes a rather useful scenario of STDIO/CONIO interoperation work: Using STDIO for screen output and CONIO for keyboard input. When cgetc() is called after cursor(1), it has to write to the screen as there's no hardware cursor on the Apple II. Those writes work as expected even in 40 column mode with active 80 column firmware as CH is only read but not written.
About all CONIO functions offering a <...>xy variant call
popa
_gotoxy
By providing an internal gotoxy variant that starts with a popa all those CONIO function can be shortened by 3 bytes. As soon as program calls more than one CONIO function this means an overall code size reduction.
