GCC 5.2.0 for OS X El Capitan

There's not a lot of added Ada goodness compared to 5.1.0, but the El
Capitan-related problem that David Botton recently encountered is fixed.

If you need PR66509 fixed and also arm-eabi support, put this compiler
on your PATH before the 5.1.0 compiler
e.g. PATH=/opt/gcc-5.2.0/bin:/opt/gcc-5.1.0/bin:/the/rest/of/your/path