Advent of bugfixes

[berni44]

11. day: 8 bugs were removed (issues 11171, 14909, 17745, 19296, 
20160, 20319, 20355, 20440)

Real fixes:
Issue 17745 - Upgrade DLang Bugzilla to 4.4.12
Issue 20160 - ThreadInfo.cleanup() clears local thread's 
registered names instead
               of "this"'s
Issue 20355 - undefined identifier U in core.atomic
Issue 20440 - Associative arrays with values whose opAssign 
doesn't return a ref don't
               support require function