AC_C_PROTOTYPES and CC=g++

[Kevin Ryde]

When CC=g++ is used, AC_C_PROTOTYPES seems to get the wrong answer.  I
think this is due to _AC_PROG_CC_STDC needing K&R style function
definitions to work before declaring the compiler ANSI capable.

I know CC=g++ is not really sensible, but there's some setups to make
"exit" work with it, so maybe it's a semi-supported feature.  In any
case, unless there's a particular reason for _AC_PROG_CC_STDC to mix
ANSI and K&R I thought to suggest:

        * lib/autoconf/c.m4 (_AC_PROG_CC_STDC): Don't require K&R definitions
        to work, only ANSI, for the benefit of CC=g++ or similar.

c.m4.ansitest.diff
Description: Source code patch