Include pthread_atfork.h to mips64 crtbegin

Bug: http://b/20339788
Change-Id: I2a8c7881f90a05ca768cb9b4c2f8b07c74c64469
diff --git a/libc/arch-mips64/bionic/crtbegin.c b/libc/arch-mips64/bionic/crtbegin.c
index 1374fea..bdd423b 100644
--- a/libc/arch-mips64/bionic/crtbegin.c
+++ b/libc/arch-mips64/bionic/crtbegin.c
@@ -92,3 +92,4 @@
 
 #include "../../arch-common/bionic/__dso_handle.h"
 #include "../../arch-common/bionic/atexit.h"
+#include "../../arch-common/bionic/pthread_atfork.h"