We should talloc_free the parser list once we're done, enabling
valgrind's leak check. Before:
[jk@pablo parser]$ valgrind ./test-null
...
==9330== HEAP SUMMARY:
==9330== in use at exit: 288 bytes in 3 blocks
==9330== total heap usage: 11 allocs, 8 frees, 1,177 bytes allocated
After:
[jk@pablo parser]$ valgrind ./test-null
...
==9940== HEAP SUMMARY:
==9940== in use at exit: 0 bytes in 0 blocks
==9940== total heap usage: 11 allocs, 11 frees, 1,177 bytes allocated
==9940==
==9940== All heap blocks were freed -- no leaks are possible