[clang][DR] Test and mark DR1479 as complete

DR: http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1479

Clang has implemented this DR as far back as I could go on compiler explorer (3.0). This patch simply adds a test case and needed comments for the update script to mark it as complete.

Differential Revision: https://reviews.llvm.org/D122620