bug #85271: sr=waterson, r={beard, jag, dbaron}, a=asa. Eliminate features of |nsXPIDLC?String| that keep it out of the string hierarchy (i.e., using assigment to rebind ownership, static |Copy| members, and |getter_Shares|), fixing some leaks in the process. git-svn-id: svn://10.0.0.236/trunk@97290 18797224-902f-48f8-a5cc-f745e15eee43