Change to exporting under 'rtslib' and 'rtslib_fb" pkg names

We should move off of 'rtslib' because we are incompatible with the
original package using this name. Export as 'rtslib_fb', and add a
warning to switch to importing by the new package name if using the old
import name.

Signed-off-by: Andy Grover <agrover@redhat.com>