[Rd] can't compile on OSX: unsetenv header issues

[Seth Falcon]

Hi,

A recent change has R failing to compile (for me) on ppc OSX 10.4.8 like this:

../../../../R-devel/src/main/datetime.c: In function `reset_tz':
../../../../R-devel/src/main/datetime.c:511: error: void value not ignored as it ought to be

I suspect there is some sort of configure magic that needs to happen
to get the POSIX compatible unsetenv on OSX.  Here's what I think is
the relevant bit from stdlib.h, but I'm hoping someone with more OSX
experience will recognize what needs to be done.

#if __DARWIN_UNIX03
int      unsetenv(const char *) __DARWIN_ALIAS(unsetenv);
#else /* !__DARWIN_UNIX03 */
void     unsetenv(const char *);
#endif /* __DARWIN_UNIX03 */


+ seth