Plugging leaks in submodule--helper.
* ab/submodule-helper-leakfix:
submodule--helper: fix a configure_added_submodule() leak
submodule--helper: free rest of "displaypath" in "struct update_data"
submodule--helper: free some "displaypath" in "struct update_data"
submodule--helper: fix a memory leak in print_status()
submodule--helper: fix a leak in module_add()
submodule--helper: fix obscure leak in module_add()
submodule--helper: fix "reference" leak
submodule--helper: fix a memory leak in get_default_remote_submodule()
submodule--helper: fix a leak with repo_clear()
submodule--helper: fix "sm_path" and other "module_cb_list" leaks
submodule--helper: fix "errmsg_str" memory leak
submodule--helper: add and use *_release() functions
submodule--helper: don't leak {run,capture}_command() cp.dir argument
submodule--helper: "struct pathspec" memory leak in module_update()
submodule--helper: fix most "struct pathspec" memory leaks
submodule--helper: fix trivial get_default_remote_submodule() leak
submodule--helper: fix a leak in "clone_submodule"