To do this we add a constructor call to UPDCRAMPTR, which is the ROM
routine that fixes up CRAM_PTR to match the screen location pointed to
by SCREEN_PTR.
This adds two additional bytes to programs using cputc() or other
routines that call it. These are in theory recoverable, but the VIC-20
does not yet free space used by constructors after the constructors
have been called.
Thanks to <greg.king5@verizon.net> (GitHub: greg-king5) for
investigating the difference in the VIC-20 KERNAL from the C64 and
proposing this solution to the problem.[1]
[1]: https://github.com/cc65/cc65/issues/946#issuecomment-538502820
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