Ensure clean builds for all compiler families

[rgrumbine]

So far, the code has been build for the last many years on Intel compilers. But a) there are multiple platforms b) they each have multiple Intel compiler suites and c) other compiler suites (e.g. Gnu) can flag different issues in the source code.

Relatedly, it's desirable for the codes to pass without comment at the highest language standard levels.
For C++ in gcc and clang:
-std=c++11 (currently used in system)
-std=c++14
-std=c++17
-std=c++20

For C in gnu:
-std=c99
-std=c11
-std=c17

For fortran:
Intel:
-std95, or -stand f95
-std03, or -stand f03
-std08, or -stand f08
-stand f18

Gnu:
-std=f95
-std=f2003
-std=f2008
-std=f2018