Use .mw-body in skins
- This helps Parsoid's output reach parity.
- Merge in conjunction with Vector: Iae873906abcd8b2a986e5f728f0ce207256de770 MonoBook: I0c889950e618b2afa6332c4c56b5531744526e72
Bug: 38726
Change-Id: Id0228fa839ef80b0b3bfee864e81f2c65963e01b