WIP check-in to allow merge of upstream changes.

indra/llinventory/llsettingssky.cpp

indra/llinventory/llsettingssky.h

indra/newview/CMakeLists.txt

indra/newview/lldensityctrl.cpp

indra/newview/lldensityctrl.h

indra/newview/llfloatereditextdaycycle.cpp

indra/newview/llpaneleditsky.cpp

indra/newview/llpaneleditsky.h

...wview/skins/default/xui/en/floater_edit_ext_day_cycle.xml

...wview/skins/default/xui/en/panel_settings_sky_density.xml

indra/newview/skins/default/xui/en/widgets/density_ctrl.xml