Sync with upstream findfp.c.

Change-Id: Ib298f46de0c4d0fd4ce0a9b456c163e8b8b06342
diff --git a/libc/stdio/fileext.h b/libc/stdio/fileext.h
index 1f2a3a3..7efff8f 100644
--- a/libc/stdio/fileext.h
+++ b/libc/stdio/fileext.h
@@ -43,6 +43,8 @@
 	pthread_mutex_t _lock; /* file lock */
 };
 
+__LIBC_HIDDEN__ extern struct __sfileext __sFext[3];
+
 #define _FILEEXT_INITIALIZER  {{NULL,0},{0},PTHREAD_RECURSIVE_MUTEX_INITIALIZER}
 
 #define _EXT(fp) ((struct __sfileext *)((fp)->_ext._base))