ANN: Cortex GNAT RTS 20180607

[Simon Wright <simon@pushface.org>]

This release doesn't change any RTS functionality; instead, it 
reorganises the structure of the source code so as to accomodate 
the changes made to keep in synchrony with compiler releases 
without using git branches.   [I'd like to shout out a big THANKS! 
to the person here who reminded me about using variant-specific 
subdirectories for the changed files. I was getting quite 
overwhelmed with running 6 parallel branches!]

This affects how you build the RTS: you must specify which release 
of the compiler you're building for, e.g.

   make RELEASE=gnat-gpl-2017

and the RTS must be installed, either with the compiler or locally 
(you can't any longer use the RTS directly in its build location).

Find at
https://github.com/simonjwright/cortex-gnat-rts/releases/tag/r20180607