Update header versions for NDK platform fixes.

Bug: http://b/28178111
Change-Id: Icd638673b409aa43a91490f77c6b4d79c9ea20d9
diff --git a/libc/include/sys/statvfs.h b/libc/include/sys/statvfs.h
index 1f00b9d..f6b9803 100644
--- a/libc/include/sys/statvfs.h
+++ b/libc/include/sys/statvfs.h
@@ -60,10 +60,10 @@
 #define ST_RELATIME    0x1000
 
 extern int statvfs(const char* __restrict _Nonnull, struct statvfs* __restrict _Nonnull)
-  __INTRODUCED_IN(21);
+  __INTRODUCED_IN(19);
 extern int statvfs64(const char* __restrict _Nonnull, struct statvfs64* __restrict _Nonnull)
   __INTRODUCED_IN(21);
-extern int fstatvfs(int, struct statvfs* _Nonnull) __INTRODUCED_IN(21);
+extern int fstatvfs(int, struct statvfs* _Nonnull) __INTRODUCED_IN(19);
 extern int fstatvfs64(int, struct statvfs64* _Nonnull) __INTRODUCED_IN(21);
 
 __END_DECLS