subnet->ip_ver & address->ip_ver cannot be IPVX_N, only IPVx_A

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
correct a long standing bug in addrv62str where indexes were not initialized

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
don't open code the type and type size of bitmap

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
add increase_bitmap & decrease_bitmap functions

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
update bitmap.h header

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
add ipv6_shift MACROS and use them;
preparation for NEXT/PREVIOUS subnet

Signed-off-by: etienne basset <etienne.basset@numericable.fr>