all: rework source tree structure

src/sys/rcu/root.zig

@@ -0,0 +1,14 @@
+//! Collection of SMR-based lock-free data structures.
+//! Note that "RCU" here does not refer to the Linux implementation, but rather
+//! as a generic term to describe concurrent data structures.
+
+const std = @import("std");
+
+pub const HashTableType = @import("hashtable.zig").TableType;
+
+/// Singly-linked list
+pub const SList = struct {
+    pub const Entry = struct {
+        next: std.atomic.Value(usize),
+    };
+};