This directory is for compilers that are ISO. Thus
if your compiler is compliant you can do

(in vcl_blah.h)

#ifdef VCL_MY_COMPILER
# include "iso/vcl_blah.h"
#elif ... other compilers
...
#endif

If you try this and it doesn't work, then your 
compiler is not ISO and you are not allowed to
modify the files in this directory to make them
work with your non-ISO compiler.

If you find that vcl/iso/vcl_blah.h is *almost*
right for your compiler, you may #include it and
then fix a few things afterwards (or before).

All of the .h files in this directory should look like this:
  #include <blah>
  #define vcl_generic_blah_STD std
  #include "../generic/vcl_blah.h"
