message: Document style a bit more.
diff: @@ -30,6 +30,7 @@ use um::d3dcommon::{
  ## Extern functions
  * The calling convention specified should be the one for 32bit. Specify `system` for stdcall and `C` for cdecl (and `fastcall` for those couple of fastcall functions out there).
  +* One parameter per line.
  ```Rust
  extern "system" {
  @@ -99,6 +100,34 @@ STRUCT!{struct GROUP_AFFINITY {
  pub type PGROUP_AFFINITY = *mut GROUP_AFFINITY;
  ```
  +## Unions
  +
  +* `UNION!` is being deprecated in favor of `UNION2!` in order to more closely align with the new untagged union feature.
  +
  +```C
  +typedef union {
  + USN_RECORD_COMMON_HEADER Header;
  + USN_RECORD_V2 V2;
  + USN_RECORD_V3 V3;
  + USN_RECORD_V4 V4;
  +} USN_RECORD_UNION, *PUSN_RECORD_UNION;
  +```
  +```Rust
  +UNION2!{union USN_RECORD_UNION {
  + [u64; 10],
  + Header Header_mut: USN_RECORD_COMMON_HEADER,
  + V2 V2_mut: USN_RECORD_V2,
  + V3 V3_mut: USN_RECORD_V3,
  + V4 V4_mut: USN_RECORD_V4,
  +}}
  +pub type PUSN_RECORD_UNION = *mut USN_RECORD_UNION;
  +```
  +
  +## Anonymous unions and structs
  +
  +* If the type `FOO` contains a single anonymous struct or union, give the anonymous struct or union a name of `FOO_s` or `FOO_u` respectively, and the field a name of `s` or `u` respectively.
  +* If the type `FOO` contains multiple anonymous structs or unions, append a number, such as `s1: FOO_s1` `s2: FOO_s2` or `u1: FOO_u1` `u2: FOO_u2`.
  +
  ## COM interfaces
  ```Rust
  