auto merge of #20443 : nikomatsakis/rust/autoderef-overloaded-calls, r=pcwalton

Use autoderef for call notation. This is consistent in that we now autoderef all postfix operators (`.`, `[]`, and `()`). It also means you can call closures without writing `(*f)()`. Note that this is rebased atop the rollup, so only the final commit is relevant.

r? @pcwalton

diff --cc src/librustc/middle/cfg/construct.rs
Simple merge

diff --cc src/librustc/middle/liveness.rs
Simple merge

diff --cc src/librustc_trans/trans/callee.rs
Simple merge

diff --cc src/librustc_typeck/check/mod.rs
Simple merge