Autoconf 2.59 breaks libstdc++ checks

[Kean Johnston]

> Then that AmigaOS ANSI/ISO C library is broken.  If you look at
> Section 7.1.4, "Use of library functions", you'll see that it's legal
> for a program to use "#undef getc" to ensure that an actual function
> is available for getc.

getc is just one example, perhaps a bad one. The point is that the
autoconf test is not trying to make sure you conform to ISO/ANSI
standards for the set of functions defined there. Its a generic
test that will fail for *any* package that uses macros to implement
what looks to the visual eye to be a function. So for example if
libz were to change such that gzrewind() was implemented in terms
of a macro, autoconf would now detect it as *MISSING*. But if you
#include <zlib.h> and "call" gzrewind() it will work, which is
ultimately what the autoconf test is trying to determine. All this
talk about standards and such, while interesting, is not germaine.

Kean