This changes the BDOS call from CPM_BDOS_CONSOLE_INPUT to
CPN_BDOS_READ_CONSOLE_BUFFER. This allows commands like ^H to delete
characters and ^C to exit to CCP. This is more like how Unix read(2)
uses canonical mode of termios to read a line.
This change has a disadvantage: the user buffer to read(2) must now be
large enough for an entire line. This is because CP/M, unlike Unix,
lacks a kernel buffer to hold the rest of the line. If you use a
buffered input library like stdio to call read(2), then it works; but
if you try to read part of a line or a single character, then it
doesn't work.
