[OE-core] [morty][PATCH v2] gcc6.4 upgrade

[Bystricky, Juro]

This was morty upgrade, which did not have those patches to begin with, I did not remove them.  The patches were not in rocko either, in the end I got them from master  (gcc6.4 was eventually removed completely),
Backporting of ARM specific patches was not the objective. ( I was not aware that 6.4 had an ARM specific regression which broke the pi3 builds).
Long story short, all patches should be there now, please review them, see the commit message for more details. 
I'll make sure all other gcc6 upgrades contain the ARM patches as well.