#warning possibly dangerous?

In utils/int8.h we currently have

/* this should be set in pg_config.h, but just in case it wasn't: */
#ifndef INT64_FORMAT
#warning "Broken pg_config.h should have defined INT64_FORMAT"
#define INT64_FORMAT "%ld"
#endif

I would like to remove this. The #warning command is not standard C.
I get a warning about it from HP's cc, and it may produce hard errors
on other non-gcc compilers with even less forgiving preprocessors.
We could just take out that one line --- but we are not in the habit of
backstopping configure/pg_config.h for any other settings, so I don't
see the point of doing it for INT64_FORMAT. I'd like to take out all
five lines.

Objections?

regards, tom lane