Naming convention for macros

[dtolnay]

The C-CASE table needs a line for macros. I believe the convention is snake_case!.

[dtolnay]

Added in f59ec10.

[ExpHP]

Should this recommendation be applied unilaterally, or is it more subtle? I've been using PascalCase! for macros that expand into types. (e.g. Array![i32; 5; 4; 3] which expands into [[[i32; 3]; 4]; 5])

[dtolnay]

Thanks! I did not consider type macros when I wrote this. I filed #145 to follow up.