commit 04102125 removed a feature, only several versions of
GDM relied on for doing the splash to login screen transition.
but it missed a few spots in the build goo and documentation. So
this commit does another pass to fully clean up any lingering
references to obsolete GDM transition code.
Splashes aren't just shown for "boot" so including "boot" in
the name isn't right. Also, right now we link against libpng
even if we don't have any splash that uses it. This is the first
step toward making libpng only get linked to graphical splashes.
We'll need to move the graphical bits to their own library to
complete the process.
Package the individual plugins as subpackages and
get the file lists up to date. Also, drop
plymouth-update-initrd %post call since it's not
meant to be used in packages
