Remove an unnecessary field from struct blist. (The comment describing
what this field represented was also inaccurate.) Suggested by: kib

In r178792, blist_create() grew a malloc flag, allowing M_NOWAIT to be
specified. However, blist_create() was not modified to handle the
possibility that a malloc() call failed. Address this omission.

Increase the width of the local variable "radix" to 64 bits. (This
matches the width of the corresponding field in struct blist.)

Reviewed by: kib
MFC after: 6 weeks