olsr: bump to version 0.6.4

Bump olsrd to version 0.6.4

Fixes:
http://autobuild.buildroot.net/results/553c8157cd83ca60475caacc119779c778806781/


which is due to the old version not being friendly with newer flex
versions.

Enabled more plugins to make it more useful.

Switch to forked mode in the init script to avoid console noise.

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