Update NetBSD timestamp to 20130923 1600UTC

This is mostly to pull in changes related to PCI device drivers.
Addresses some other minor issues too, like issue #40.
Source for buildrump.sh git rev 448420054e0e63f40006f03ecba93fc369aa6a58
new bus.h, contains BUS_DMA_TAG_IS_VALID for amd64
Source for buildrump.sh git rev 1c25864dd11727b33490f943f6418f39d082f894