Allow allocation of any 0 sized type (not just void)

std/mem.zig

@@ -34,7 +34,7 @@ pub const Allocator = struct {
     /// Call `destroy` with the result
     pub fn create(self: *Allocator, init: var) Error!*@typeOf(init) {
         const T = @typeOf(init);
-        if (@sizeOf(T) == 0) return &{};
+        if (@sizeOf(T) == 0) return &T{};
         const slice = try self.alloc(T, 1);
         const ptr = &slice[0];
         ptr.* = init;