🚀 go-pugleaf

The meaning of __STDC__ is defined by the ANSI C standard
for ANSI C compilers.

As for compilers not precisely supporting ANSI C, it means whatever we
decide it means.  The question is, what is the useful thing to do with
it?  For GCC, I decided to define __STDC__ as 1 when the ANSI C
features (prototypes, etc.) are available, and not define it
otherwise.  I am not sure this is the best possible way, but I'm also
not sure another way is better.  Unless/until I'm convinced to change
it for all machines, I plan to keep it this way on all machines.