-lrt is now added as needed in each module Makefile, but not directly in
the library. Furthermore, the Makefiles add -lrt only if the platform is
Linux.
* libowlps, libowlps-client & owlps-listener:
Add Makefiles to compile for OpenWrt 10.03 (Backfire). (owlps-client had
one already.)
* libowlps & libowlps-client:
Update the Makefiles for OpenWrt 8.09 (Kamikaze).