Re-fix leak in source.c (open_source_file).

Leak fixed in '8e6a5953e1d Fix 4K leak in open_source_file' has been partially
undone by '2179fbc36d23 Return scoped_fd from open_source_file'. Re-add the
transfer of current s->fullname to the unique_xmalloc_ptr fullname given to
find_and_open_source.
2 files changed