Code review comment for ~info-martin-konrad/epics-base:simplify-compiler-specific-macros

Doing this on 3.15 is going to be a problem, both https://epics.anl.gov/base/R3-15/index.php and https://jenkins.aps.anl.gov/job/epics-base-3.15-vx55/ show that we still support VxWorks 5.5 on the 3.15 branch, and that comes with gcc-2.96+. Sorry.

Doing it on 7.0 would be fine by me though.