The previous names (RGBA32 and RGB32) were misleading since that's not
the actual byte order in memory. The new names reflect exactly how the
color values get laid out in bitmap data.
Now that WindowServer broadcasts the system theme using an anonymous
file, we need clients to pledge "recvfd" so they can receive it.
Some programs keep the "shared_buffer" pledge since it's still used for
a handful of things.
