Fix issue 10165 (rework of PR #1302)

http://issues.dlang.org/show_bug.cgi?id=10165
Issue 10165: No syntax to create thread-local shared variables

Adds `UnqualRef` templated alias/struct that is similar to Rebindable but
strips away all qualifiers completely (including shared)

An alternative to https://github.com/D-Programming-Language/phobos/pull/1302
Nitpick, but just use `attribute:` syntax to eliminate the extra level of indentation?