Make a start on SSE for x86 guest.


git-svn-id: svn://svn.valgrind.org/vex/trunk@602 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/main/vex_main.c b/priv/main/vex_main.c
index b6e70b6..4fb4860 100644
--- a/priv/main/vex_main.c
+++ b/priv/main/vex_main.c
@@ -125,6 +125,7 @@
    vassert(1 == sizeof(Bool));
    vassert(4 == sizeof(Addr32));
    vassert(8 == sizeof(Addr64));
+   vassert(16 == sizeof(U128));
 
    vassert(sizeof(void*) == 4 || sizeof(void*) == 8);
    vassert(sizeof(void*) == sizeof(int*));