[bonninr]

Fixes the layout part of #493.

• Organ settings opens 780 wide, enough for each keyboard's row on the MIDI tab at full width: name, channel, device and "Range, transpose...". The height stays 560, which a 720-pixel screen holds whole; the tabs scroll.
• In a narrower window the device box gives way first, down to 140, and the range button keeps its 160. Players who opened Organ settings before keep their saved size, the old 660 wide, so this is what they see.

Checked in the program on Windows, GrandOrgue demo, Organ settings > MIDI:

Window	Before	After
Saved size 662 x 588 (the old default, as kept in dialogs.txt)	the three "Range, transpose..." buttons about 75 px wide, their text shrunk to a few pixels	the buttons read "Range, transpose..." in full; the device boxes are narrower
First opening, no saved size	as above	798 x 627 on screen, every row at full width, the note beside "Clear default" whole

The size the player leaves the window at is kept since 0.7.3: opened, resized, closed and reopened at the new size on Windows, and again after a restart. The report is from macOS, where this is still to be checked.

mp_tests --no-perf: 300 run, 0 failed.