Originally the Apple II had a 64 char set and used the upper two bits to control inverse and blinking. The Apple //e brought then an alternate char set without blinking but more individual chars. However, it does _not_ contain 128 chars and use the upper bit to control inverse as one would assume. Rather it contains more than 128 chars - the MouseText chars. And because Apple wanted to provide as much backward compatibility as possible with the original char set, the alternate char set has a rather weird layout for chars > 128 with the inverse lowercase chars _not_ at (normal lowercase char + 128).
So far the Apple II CONIO implementation mapped chars 128-255 to chars 0-127 (with the exception of \r and \n). It made use of alternate chars > 128 transparently for the user via reverse(1). The user didn't have direct access to the MouseText chars, they were only used interally for things like chline() and cvline().
Now the mapping of chars 128-255 to 0-127 is removed. Using chars > 128 gives the user direct access to the "raw" alternate chars > 128. This especially give the use direct access to the MouseText chars. But this clashes with the exsisting (and still desirable) revers(1) logic. Combining reverse(1) with chars > 128 just doesn't result in anything usable!
What motivated this change? When I worked on the VT100 line drawing support for Telnet65 on the Apple //e (not using CONIO at all) I finally understood how MouseText is intended to be used to draw arbitrary grids with just three chars: A special "L" type char, the underscore and a vertical bar at the left side of the char box. I notice that with those chars it is possible to follow the CONIO approach to boxes and grids: Combining chline()/cvline() with special CH_... char constants for edges and intersections.
But in order to actually do so I needed to be able to define CH_... constants that when fed into the ordinary cputc() pipeline end up as MouseText chars. The obvious approach was to allow chars > 128 to directly access MouseText chars :-)
Now that the native CONIO box/grid approach works I deleted the Apple //e proprietary textframe() function that I added as replacement quite some years ago.
Again: Please note that chline()/cvline() and the CH... constants don't work with reverse(1)!
We want to add the capability to not only get the time but also set the time, but there's no "setter" for the "getter" time().
The first ones that come into mind are gettimeofday() and settimeofday(). However, they take a struct timezone argument that doesn't make sense - even the man pages says "The use of the timezone structure is obsolete; the tz argument should normally be specified as NULL." And POSIX says "Applications should use the clock_gettime() function instead of the obsolescent gettimeofday() function."
The ...timeofday() functions work with microseconds while the clock_...time() functions work with nanoseconds. Given that we expect our targets to support only 1/10 of seconds the microseconds look preferable at first sight. However, already microseconds require the cc65 data type 'long' so it's not such a relevant difference to nanoseconds. Additionally clock_getres() seems useful.
In order to avoid code duplication clock_gettime() takes over the role of the actual time getter from _systime(). So time() now calls clock_gettime() instead of _systime().
For some reason beyond my understanding _systime() was mentioned in time.h. _systime() worked exactly like e.g. _sysremove() and those _sys...() functions are all considered internal. The only reason I could see would be a performance gain of bypassing the time() wrapper. However, all known _systime() implementations internally called mktime(). And mktime() is implemented in C using an iterative algorithm so I really can't see what would be left to gain here. From that perspective I decided to just remove _systime().
As discussed in https://github.com/cc65/cc65/pull/452 after my premature merge the two functions in question don't work as expected.
Additionally I adjusted several style deviations in the pull request in question.
