Unregister pthread_atfork handlers on dlclose()

Bug: http://b/20339788
Change-Id: I874c87faa377645fa9e0752f4fc166d81fd9ef7e
diff --git a/libc/arch-common/bionic/crtbegin.c b/libc/arch-common/bionic/crtbegin.c
index fa9f3f3..c46405c 100644
--- a/libc/arch-common/bionic/crtbegin.c
+++ b/libc/arch-common/bionic/crtbegin.c
@@ -59,6 +59,7 @@
 
 #include "__dso_handle.h"
 #include "atexit.h"
+#include "pthread_atfork.h"
 #ifdef __i386__
 # include "../../arch-x86/bionic/__stack_chk_fail_local.h"
 #endif