Created the Structure.test_bug_22861_PDB_writing_chainID_fail system test.
This is to catch bug #22861 (https://gna.org/bugs/?22861), the chain IDs in the structure.write_pdb user function PDB files are incorrect after calling structure.delete.
Authored by: bugman 2014-10-23
Parent: [r26379]
Child: [r26381]
