Macro webrender::enumerate_interners

macro_rules! enumerate_interners {
    ($macro_name: ident) => { ... };
}

Meta-macro to enumerate the various interner identifiers and types.

IMPORTANT: Keep this synchronized with the list in mozilla-central located at gfx/webrender_bindings/webrender_ffi.h

Note that this could be a lot less verbose if concat_idents! were stable. :-(