Since comedi_ioctl() calls libc_error() to set __comedi_errno to errno
(and possibly print an error message), there is no need for callers of
comedi_ioctl() to set __comedi_errno immediately afterwards. But
comedi_command(), comedi_command_test(), and comedi_do_insnlist()
currently do that. Remove the unneeded setting of __comedi_errno in
those functions.
Also, comedi_command() and comedi_command_test() check __comedi_errno
regardless of whether comedi_ioctl() returnis an error, and possibly
modify the error code to an internal comedi error. Change them to only
do that if comedi_ioctl() returns an error, because __comedi_errno might
contain a stale value.
6458b08e56