Leftmouse select option doesn't work with "Emulate 3 button mouse" option.
The latter maps middle mouse to ALT+leftmouse, frustrating loop select for
example.
Add tooltip to say this, made option to disable automatic on load (version
check) and made buttons redraw to show option being disabled.
Note; wrapping middle mouse to ALT+RMB will frustrate 1 button mices... the
current code for leftmouse-select is a hack at best, better do this good
when we have proper event handlers system.
e2d4750f41