Use inout for ref returning members in std.container.array

For motivation see 

http://forum.dlang.org/thread/agyeejbrpotpjrecepyl@forum.dlang.org#post-wysehvbsfnezfozsagpl:40forum.dlang.org
Does inout on a constructor have any meaningful semantics yet? I remember seeing a DIP on it, but don't remember the outcome. @9rnsr?