configure.in: bumped version number to 0.8.6
configure.in: bumped version number to 0.8.6

The jump in version numbers has been suggested by Raul Fuentes, see
http://dev.eclipse.org/mhonarc/lists/tinydtls-dev/msg00005.html

cetic/tinydtls,cetic/tinydtls,cetic/tinydtls,cetic/tinydtls