create more than three buflist items by using buflist.look.use_items

[pascalpoitras]

Feature description

the option buflist.look.use_items dictate how many buflist items we want to use in a range of 3. I know this option was create to speed the buflist for user that use only, for example, one item instead of 2 or 3. But It would be great if we could set it to more than 3, and if we did, it create more buflist items. So, if we set it to 5 it create buflist, buflist2, buflist3, buflist4 and buflist5