userspace: Add basic find utility

This is mostly working but is missing -exec and -ok support. It can
search files though :^)

userspace/programs/find/Node.h

@@ -0,0 +1,69 @@
+#pragma once
+
+#include "Token.h"
+
+#include <sys/types.h>
+#include <time.h>
+
+struct Node
+{
+	enum class Type
+	{
+		NOD_AND,    NOD_OR,      NOD_NOT,
+		NOD_NAME,   NOD_INAME,   NOD_PATH,
+		NOD_NOUSER, NOD_NOGROUP, NOD_MOUNT,
+		NOD_XDEV,   NOD_PRUNE,   NOD_PERM,
+		NOD_TYPE,   NOD_LINKS,   NOD_USER,
+		NOD_GROUP,  NOD_SIZE,    NOD_ATIME,
+		NOD_CTIME,  NOD_MTIME,   NOD_EXEC,
+		NOD_OK,     NOD_PRINT,   NOD_PRINT0,
+		NOD_NEWER,  NOD_DEPTH,
+	};
+
+	enum class Comp
+	{
+		Eq, Gt, Lt
+	};
+
+	Type type;
+	union {
+		// AND, OR
+		struct {
+			Node* lhs;
+			Node* rhs;
+		} bin_op;
+		// NOT
+		Node* child;
+		// NAME, INAME, PATH
+		const char* pattern;
+		// PERM, TYPE
+		mode_t mode;
+		// USER
+		uid_t uid;
+		// GROUP
+		gid_t gid;
+		// LINKS, SIZE, ATIME, CTIME, MTIME
+		struct {
+			uint64_t value;
+			Comp comp;
+		} n;
+		// EXEC, OK
+		struct {
+			const char* args;
+			size_t count;
+		} args;
+		// NEWER
+		timespec mtime;
+	} as;
+
+	Node(Type type, decltype(Node::as) as);
+	Node(Type type);
+};
+
+extern bool g_mount_specified;
+extern bool g_xdev_specified;
+extern bool g_prune_specified;
+extern bool g_depth_specified;
+
+Node* compile_tokens(BAN::Span<const Token>);
+bool evaluate_node(Node*, const char* path, struct stat&);