Description: Fix Xen block IO merge-ability calculation
References:
 https://xenbits.xen.org/xsa/advisory-229.html
Notes:
Bugs: #866511
upstream: released (4.13-rc6) [462cdace790ac2ed6aad1b19c9c0af0143b6aab0]
4.9-upstream-stable: released (4.9.45) [6c7f3756d072050d612e5c5c04108f90f1985435]
3.16-upstream-stable: released (3.16.48) [f664b0113d2bb8d4bcdf5d03b72eb4c433ded452]
3.2-upstream-stable: released (3.2.93) [33bab9221e22bab4ddc167f6c49b6ca9c35c2ccf]
sid: released (4.12.12-1)
4.9-stretch-security: released (4.9.30-2+deb9u4) [bugfix/all/xen-fix-bio-vec-merging.patch]
3.16-jessie-security: released (3.16.43-2+deb8u4) [bugfix/all/xen-fix-bio-vec-merging.patch]
3.2-wheezy-security: released (3.2.93-1)