#18 Unnecessary mouse format option in mummerplot

[Adam Phillippy]

set mouse format "%.0f"
^
"out.gp", line 11: unrecognized option - see 'help set'.

"set mouse format" Causes a warning with gnuplot v5 when user selects a non-interactive plot type.

The whole mummerplot script needs retesting for gnuplot v5 and newer versions of perl.