Avoid writing xvgr formatting with -xvg none

Avoid writing xvgr formatting with -xvg none

Several tools were writing xvgr formatting code directly
to output files, even when the users selects -xvg none as
a command line option.

Fixes #1407, #1479.

Change-Id: I1db10c2ad7455332e2a415a922885cddaec5efd1