Help browser: Cosmetic changes in the GUI prefs, add a warning about the impact of help browser settings on startup times.

Changes in the search path (prefs dialog) don't really need a relaunch of the application to take effect, change the tooltips in the translations accordingly.

Fix up misleading tooltips for the Ok/Apply/Close buttons of the Preferences dialog. These apply to the prefs dialog as a whole, not just to the audio properties.

port moonlib/mknob, and fix an iemgui dialog bug with empty strings not getting changed to zeroes for numeric fields

This automatically picks the right zoom level to make the patch fill the window as much as possible. Also fixes a missing call to pdgui.gui_canvas_get_scroll in the m.view.zoomreset menu command which caused the viewport not to be updated properly after resetting the zoom level in canvas windows.