Update header versions for NDK platform fixes.

Bug: http://b/28178111
Change-Id: Icd638673b409aa43a91490f77c6b4d79c9ea20d9
diff --git a/libc/include/search.h b/libc/include/search.h
index 1ac6d21..dc160e9 100644
--- a/libc/include/search.h
+++ b/libc/include/search.h
@@ -38,10 +38,10 @@
   __INTRODUCED_IN(21);
 
 void* tdelete(const void* __restrict, void** __restrict, int (*)(const void*, const void*))
-  __INTRODUCED_IN(21);
-void tdestroy(void*, void (*)(void*)) __INTRODUCED_IN(21);
-void* tfind(const void*, void* const*, int (*)(const void*, const void*)) __INTRODUCED_IN(21);
-void* tsearch(const void*, void**, int (*)(const void*, const void*)) __INTRODUCED_IN(21);
+  __INTRODUCED_IN(16);
+void tdestroy(void*, void (*)(void*)) __INTRODUCED_IN(16);
+void* tfind(const void*, void* const*, int (*)(const void*, const void*)) __INTRODUCED_IN(16);
+void* tsearch(const void*, void**, int (*)(const void*, const void*)) __INTRODUCED_IN(16);
 void twalk(const void*, void (*)(const void*, VISIT, int)) __INTRODUCED_IN(21);
 
 __END_DECLS