Add output line pacing support (delay before sending LF)

New LINEDELAY and LINEDELAY:n @-codes
Another way to pace the terminal output of long display (e.g. ANSI) files. LINEDELAY enables a 1/10th of a second delay before the sending of all LF chars. LINEDELAY:n sets the line_delay duration explicitly to a value in 1/100ths of a second units. So LINEDELAY and LINEDELAY:10 are equivalent. LINEDELAY:0 turns line-pacing off. The original line pacing value is always restored after a printfile/putmsg operation.

New JS console.line_delay property (milliseconds) to control via JS. Setting this to a really high value would be bad. Some range enforcement should be added to this and many other console control values (TODO).