Allow storing a result value for a token from a lexer code block

spec/test_lexer_result_value.d

@@ -0,0 +1,20 @@
+import testparser;
+import std.stdio;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = `x`;
+    auto parser = new Testparser.Parser(input);
+    assert(parser.parse() == true);
+    assert(parser.result == 1u);
+
+    input = `fabulous`;
+    parser = new Testparser.Parser(input);
+    assert(parser.parse() == true);
+    assert(parser.result == 8u);
+}