The checks used to be in update.c, but as they are related to
the intended file operation, they are better placed in fileio.c.
The checks affected are to refuse 'm' on output (file write),
and 'd', 'h', 'o', and 'b' formats on input (file read).
The file format specifiers 'h', 'd', 'o', and 'b' are only valid for
outputting data. Reject them with a proper error message when
attempting to use them for input.
Joerg Wunsch
Stefan Rueger
MCUdude
Marius Greuel