RFC acceptable handling of VLAs across toolchains

[Tyler Retzlaff]

hi folks,

i'm seeking advice. we have use of VLAs which are now optional in
standard C. some toolchains provide a conformant implementation and msvc
does not (and never will).

we seem to have a few options, just curious about what people would
prefer.

* use alloca

* use dynamically allocated storage

* conditional compiled code where the msvc leg uses one of the previous
  two options

i'll leave it simple for now, i'd like to hear input rather than provide
a recommendation for now.

thanks!