Finish <search.h>.

I'm unable to find a bug, but we've had requests for this internally
once or twice (though I pointed those folks at the STL), and there's
code we build for the host or in our bootloaders that would use this,
and there's reasonable-looking FreeBSD implementation ready and waiting.

Bug: N/A
Test: ran tests
Change-Id: I6ddee4b71bea4c22ed015debd31d3eaac4fcdd35
diff --git a/libc/bionic/tdestroy.cpp b/libc/bionic/tdestroy.cpp
index 95c3e64..2968ff9 100644
--- a/libc/bionic/tdestroy.cpp
+++ b/libc/bionic/tdestroy.cpp
@@ -14,10 +14,15 @@
  * limitations under the License.
  */
 
-#define _SEARCH_PRIVATE
 #include <search.h>
 #include <stdlib.h>
 
+struct node_t {
+  char* key;
+  struct node* llink;
+  struct node* rlink;
+};
+
 // Destroy a tree and free all allocated resources.
 // This is a GNU extension, not available from BSD.
 void tdestroy(void* root, void (*destroy_func)(void*)) {