Remove unnecessary 'extern's.

Change-Id: Iba2b3fb6ff88e504f1657b915120ae43d58a1e03
diff --git a/libc/include/sys/statvfs.h b/libc/include/sys/statvfs.h
index f6b9803..af1b9c0 100644
--- a/libc/include/sys/statvfs.h
+++ b/libc/include/sys/statvfs.h
@@ -59,12 +59,12 @@
 #define ST_NODIRATIME  0x0800
 #define ST_RELATIME    0x1000
 
-extern int statvfs(const char* __restrict _Nonnull, struct statvfs* __restrict _Nonnull)
+int statvfs(const char* __restrict _Nonnull, struct statvfs* __restrict _Nonnull)
   __INTRODUCED_IN(19);
-extern int statvfs64(const char* __restrict _Nonnull, struct statvfs64* __restrict _Nonnull)
+int statvfs64(const char* __restrict _Nonnull, struct statvfs64* __restrict _Nonnull)
   __INTRODUCED_IN(21);
-extern int fstatvfs(int, struct statvfs* _Nonnull) __INTRODUCED_IN(19);
-extern int fstatvfs64(int, struct statvfs64* _Nonnull) __INTRODUCED_IN(21);
+int fstatvfs(int, struct statvfs* _Nonnull) __INTRODUCED_IN(19);
+int fstatvfs64(int, struct statvfs64* _Nonnull) __INTRODUCED_IN(21);
 
 __END_DECLS