Store bufpool generations list as an array

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Make bufpool generations store their member meshes in an array

This leaves bufpool.c and mesh.c juuust a bit less coupled, and clears the way
to kill linked lists.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Kill util.h linked lists

The implementation had a few warts anyway, and we can do without them now.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>