classpath: add config.rpath

Add config.rpath from upstream CVS to avoid autoreconf errors. Fixes:
http://autobuild.buildroot.net/results/e88/e88b77b28e9a0f1d2960aaa782ec0cbfd4e5e451/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>