incorrect logscale mapping, off by one step

[x42]

https://github.com/drobilla/jalv/blob/e7992e2c48fb558f0e58099b1e98b4d45fbb58ba/src/jalv_qt.cpp#L566

This does not match the spec at http://lv2plug.in/ns/ext/port-props/#rangeSteps

value = lower * pow(upper / lower, step / (steps - 1))

"This value indicates into how many evenly-divided points the (control) port range should be divided for step-wise control." note: points - not steps between points, are inclusive. hence a -1 is needed.

[x42]

All FAUST generated LV2s do have rangeSteps. And now https://github.com/x42/dpl.lv2 has too (but that's not a QT UI)

[drobilla]

Fixed in b1fb68f, thanks.