Add missing includes.

Change-Id: Ibf549266a19a67eb9158d341a69dddfb654be669
diff --git a/linker/dlfcn.cpp b/linker/dlfcn.cpp
index 7ef94c0..9a8dbc9 100644
--- a/linker/dlfcn.cpp
+++ b/linker/dlfcn.cpp
@@ -20,6 +20,7 @@
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <android/dlext.h>
 
 #include <bionic/pthread_internal.h>