Add MarshalIn and Out instances for Double.
Add MarshalIn and Out instances for Double.

Ignore-this: 4213d0d9748c53309928fd2cd7091b7

darcs-hash:20120604175008-4d2ae-692207296c996662ae9d124049a310fd9964c6d2

johntyree/HsQML,johntyree/HsQML