* libc/stdio/vsprintf.c (vsprintf, _vsprintf_r): Set _file fd to
-1 to be sure it cannot later match a valid file fd causing
isatty() to return 1.
* libc/stdio/asprintf.c (asprintf, _asprintf_r): Ditto.
* libc/stdio/sprintf.c (sprintf, _sprintf_r): Ditto.
* libc/stdio/vasprintf.c (vasprintf, _vasprintf_r): Ditto.
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