* initialize XColor/XftColor
this does not change behavior, but avoids passing uninitialized data to X/Xft functions
* gui, x11: move have_argb_visual to x11 files
this variable only has meaning with respect to X11
* x11: clear have_argb_visual if the setting changes to false
otherwise, we may try to use colors with alpha when we no longer requested a 32-bit visual
* x11: premultiply alpha of background colors
* x11: clean up set_foreground_color a bit
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Co-authored-by: bi4k8 <bi4k8@github>
these settings are used for GUI builds as well as ncurses builds, and if we support colors in console and HTTP output, will be used there too
colors really are essential to what Conky does, even if some outputs don't support them, so it makes sense to build support for them unconditionally