[CentOS] Good work, Red Hat!

Delivered as per https://access.redhat.com/articles/3311301. This is good news. Backporting those updates across three gcc versions does not look like the easiest exercise to me.

$ rpm -qp --changelog gcc-4.4.7-18.el6_9.2.x86_64.rpm |head -n 6
* Wed Jan 31 2018 Jeff Law <law at redhat.com> 4.4.7-18.2
- Fix indirect_jump/tablejump patters for retpolines (#1535656)

* Tue Jan 23 2018 Jeff Law <law at redhat.com> 4.4.7-18.1
- Retpoline support (#1535656)

$ rpm -qp --changelog kernel-2.6.32-696.23.1.el6.x86_64.rpm
...
* Sat Feb 10 2018 Jan Stancek <jstancek at redhat.com> [2.6.32-696.23.1.el6]
- [scsi] avoid a permanent stop of the scsi device's request queue (Ewan Milne) [1519857 1513455]
- [x86] retpoline/hyperv: Convert assembler indirect jumps (Waiman Long) [1543022 1535645]
- [x86] spec_ctrl: Upgrade GCC retpoline warning to an error for brew builds (Waiman Long) [1543022 1535645]
- [x86] retpoline: Don't use kernel indirect thunks in vsyscalls (Waiman Long) [1543022 1535645]
- [x86] spec_ctrl: Add a read-only retp_enabled debugfs knob (Waiman Long) [1543022 1535645]
...