XENBUS #32 XENVIF #35

XENBUS
Fix RangeSet cursor problem
Add magic number and bounds checking...

XENVIF
Cope with GranterPermitAccess() failing
Fix stupid typo (and add an error warning)
Remove some debug spew on grant table allocation failures

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Merge pull request #51 from pauldu/master

XENBUS #32 XENVIF #35