Implement unchainXDirect_ARM64.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2822 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/main_main.c b/priv/main_main.c
index 2ca1df1..93ca478 100644
--- a/priv/main_main.c
+++ b/priv/main_main.c
@@ -1048,6 +1048,8 @@
          unchainXDirect = unchainXDirect_AMD64; break;
       case VexArchARM:
          unchainXDirect = unchainXDirect_ARM; break;
+      case VexArchARM64:
+         unchainXDirect = unchainXDirect_ARM64; break;
       case VexArchS390X:
          unchainXDirect = unchainXDirect_S390; break;
       case VexArchPPC32: