Simple test extensions. echos input back to output. With some printfs

dover:simple-osquery-test-extension seph$ ./osqueryd-4.0.2 -S --allow-unsafe --extension build/simple-darwin.ext 
Using a virtual database. Need help, type '.help'
osquery> select * from test_table where input = "hello";
generate called
Starting on constraint #0 -- hello
Done. Processed 1 constraints
+-------+-----+--------+
| input | num | output |
+-------+-----+--------+
| hello | 0   | hello  |
+-------+-----+--------+