Some typos in draft 2

Hi,

not sure whether they've been discovered yet, but here are some small
typos in the virtio v1.0 draft 2:

- Chapter 5.1.6 Device Operation:
  "In each case, the packet itself is preceeded by a header"
  ==> s/preceeded/preceded/

- In the footnote on page 58 (chapter 5.1.6.4.3):
  "Since there are no guarentees, it can use a hash filter ..."
  ==> s/guarentees/guarantees/

- Chapter 5.2.7.1 Legacy Interface: Device Operation (page 65):
  "... this request acts as a barrier and that all preceeding requests
  SHOULD be complete ..."
  ==> s/preceeding/preceding/

 Thomas