Changed cncheckc() interface so that it is 8-bit clean - return -1 instead of 0 if there is no input.
Changed cncheckc() interface so that it is 8-bit clean - return -1
instead of 0 if there is no input.

pcvt_drv.c:
Partially fixed pccncheckc().  It returned a boolean value instead of
the character that it fetches from the input fifo (if any).  I think
it still discards characters after the first for multi-char input.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase