Add forked Maatkit tools in bin/ and their tests in t/.

t/pt-query-advisor/samples/issue-950.sql

@@ -0,0 +1,11 @@
+use test;
+create table L (
+  l_id int not null primary key
+);
+insert into L(l_id) values(1),(2),(3);
+
+create table R (
+  r_id int not null primary key,
+  r_other int NULL -- notice that this is NULL-able
+);
+insert into R(r_id, r_other) values(1, 5), (2, NULL);