Run rustfmt on tests/codegen/.

Except for `simd-intrinsic/`, which has a lot of files containing
multiple types like `u8x64` which really are better when hand-formatted.

There is a surprising amount of two-space indenting in this directory.

Non-trivial changes:
- `rustfmt::skip` needed in `debug-column.rs` to preserve meaning of the
  test.
- `rustfmt::skip` used in a few places where hand-formatting read more
  nicely: `enum/enum-match.rs`
- Line number adjustments needed for the expected output of
  `debug-column.rs` and `coroutine-debug.rs`.

tests/codegen/force-frame-pointers.rs

@@ -1,6 +1,6 @@
 //@ compile-flags: -C no-prepopulate-passes -C force-frame-pointers=y -Copt-level=0
 
-#![crate_type="lib"]
+#![crate_type = "lib"]
 
 // CHECK: attributes #{{.*}} "frame-pointer"="all"
 pub fn foo() {}