Creation of a new system test test_read_xyz_internal1().
This is Han's patch http://gna.org/task/download.php?file_id=13143 attached to the task
http://gna.org/task/?7404.
In order to create a system test for reading the xyz file, a new function
'test_read_xyz_internal1()' has been generated in the xyz/test_suite/system_tests/structure.py. It
is based on the function 'test_read_pdb_internal1()'.
