Which standards are allowed when contributing?

[zerothi]

In #197 a possible solution to check for NAN is the use of IEEE standard modules.

However, this opens the question of which standards and which practices are allowed in LAPACK?

There are many possibilities, but I think it would be nice to have some kind of guideline:

Just to name a few things:

1. Modules
2. OpenMP (there are OpenMP calls here and there...)
3. Free-form codes, etc.

[martin-frbg]

Further to this, the "recent" addition of the 2stage symmetric eigenvalue routines in 3.7.0 introduced a dependency on OpenMP4, breaking compilation with older compilers (e.g. gcc earlier than 4.9) that may still be in use e.g. in "Enterprise"-category linux distributions. In https://github.com/xianyi/OpenBLAS/pull/1460/commits/eaab622f0393590e5ad12298b9fd8739553c591f I have worked around this for OpenBLAS, but I am not sure if this is an ideal (or even adequate) solution.