Vectors are needed by the CPU, but they don't need to be accessed by Rockbox.
Without the KEEP(), they can be removed when liking with --gc-sections,
creating a broken binary without any warnings. This tells the linker to not
remove them. It should enable use of --gc-sections for all targets. When not
using --gc-sections, this does not change the binary.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31351 a1c6a512-1295-4272-9138-f99709370657
