latest fclose.c evokes new warning/error

[Jim Meyering]

Hi Eric,

I've just tried the latest from gnulib in coreutils,
and bootstrap+build failed with this:

    fclose.c: In function 'rpl_fclose':
    fclose.c:33:7: error: variable 'saved_errno' set but not used 
[-Werror=unused-but-set-variable]
    cc1: all warnings being treated as errors

Isn't that highlighting a real bug?  Currently, in the !WINDOWS_SOCKETS code,
rpl_fclose may return 0 in spite of a preceding failed fflush.