The main motivation for this series is to eliminate some backcompat
logic in the crypto code only needed for RHEL-7. I take the opportunity
to also bump the min required versions of glib, gcc and clang since we
have dropped many distros since they were last bumped.
There are possibly some more cleanups that can be done as a side effect
of these new min versions, but I leave that for other interested people
to look at.
One that might be intesting is switching from std=gnu99 to gnu11 since
we're no longer constrainted by the 4.8.x vintage GCC which marked gnu11
as experimental (see 7be41675f7cb16be7c8d2554add7a63fa43781a8)