std: Drop struct prefixes in FreeBSD siginfo
std: Drop struct prefixes in FreeBSD siginfo

I'm not sure this prefix-free style is a good idea, but let's roll with
it for the moment.

andrewrk/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,zig-lang/zig,zig-lang/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig