Initial support for multiple variable declarations.

Before:
  SomeType aaaaaaaaaaaaaaaaa = aaaaaa->aaaaaaaaaaaaaaaaa(),
      aaaaaaaaaaa = aaaaaa->aaaaaaaaaaa();
After:
  SomeType aaaaaaaaaaaaaaaaa = aaaaaa->aaaaaaaaaaaaaaaaa(),
           aaaaaaaaaaa = aaaaaa->aaaaaaaaaaa();