Hexagon: new PGI compiler and TotalView debugger versions

PGI compiler version 15.3.0 has been installed on hexagon. Version 14.9.0 is still the default, but we kindly urge you to try out latest installed version. List of changes, enhancements you'll find here:
From autumn, new Cray compiled libraries for PGI will not support anything below PGI 15.x.

A newer version - 8.15.4 - of TotalView debugger is installed on hexagon, version 8.15.0 being currently the default.