OMPD: 5.5.8 Display Control Variables

[Mohamed Atef via Gcc]

To implement this
<https://www.openmp.org/spec-html/5.1/openmpsu247.html#x312-4810005.5.8>,
should I add a function in the runtime to dump all the
environment variables. Or should I use variables from helper functions?
To make the icv-name=icv-value pair I think it will be too costly
to use helper functions.