nipapd: enable search on prefix-length
nipapd: enable search on prefix-length

This enables search based on prefix-length as a match. It's using the
masklen() function in Postgres to do this and there is currently no
functional index on that so it might be slow.

Fixes #847.

SoundGoof/NIPAP,fredsod/NIPAP,bbaja42/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,garberg/NIPAP,bbaja42/NIPAP,garberg/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,garberg/NIPAP,ettrig/NIPAP,SoundGoof/NIPAP,SoundGoof/NIPAP,SoundGoof/NIPAP,SpriteLink/NIPAP,fredsod/NIPAP,SpriteLink/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,ettrig/NIPAP,garberg/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,fredsod/NIPAP,SoundGoof/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,garberg/NIPAP,fredsod/NIPAP,SpriteLink/NIPAP,fredsod/NIPAP,fredsod/NIPAP,ettrig/NIPAP