remove the (namespace) type and make every file an empty struct

[andrewrk]

closes #1047

also struct types get fully qualified names, and function symbol names become fully qualified (extern and export being exceptions of course)

pub works on struct decls now

• test on linux
• test on macos
• test on windows

@tgschultz this has some serialization implications regarding @typeName:

const std = @import("std");
const os = std.os;

comptime {
    @compileLog(@typeName(os.File)); // "std.os.file.File"
}

[andrewrk]

After this is merged, the "index.zig" convention is deprecated. The new pattern is the one set by

• std/os/darwin.zig (and corresponding std/os/darwin/ folder)
• std/event.zig (and corresponding std/event/ folder)

[andrewrk]

Never mind what I said about @typeName. That's going to remain the same. Only function symbol names and compile error messages will be affected.