Add specific shader for the moon to allow different rendering at day vs night.

indra/llrender/llshadermgr.cpp

indra/newview/app_settings/logcontrol.xml

indra/newview/app_settings/settings.xml

.../newview/app_settings/shaders/class1/windlight/moonF.glsl

.../newview/app_settings/shaders/class1/windlight/moonV.glsl

indra/newview/lldrawpoolwlsky.cpp

indra/newview/llsky.cpp

indra/newview/llsky.h

indra/newview/lltoolgun.cpp

indra/newview/llviewershadermgr.cpp

indra/newview/llviewershadermgr.h

indra/newview/llvosky.cpp

indra/newview/llvosky.h