qemu-io: Verify read data by patterns (Kevin Wolf)

This patch adds a -P option to read and readv which allows to compare the read
data to a given pattern. This can be used to verify data written by write -P.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7182 c046a42c-6fe2-441c-8c8c-71466251a162
