Checking for ANSI-headers only

[Ralf Corsepius]

Hi,

An astonishingly simple question, I haven't found an answer to:

How to let autoconf check for it's predefined list of ansi-headers only?

AC_CHECK_HEADERS
AC_PROG_CC
violates autoconf's documentation and produces invalid shell code.

AC_PROG_CC 
alone doesn't trigger to pull-in the "check for ansi-headers".

AC_CHECK_HEADERS(unistd.h)
duplicates the check for unistd.h.

Am I missing something?

TIA,
        Ralf