Revert "UseListOrder: Remove move assignment"
Revert "UseListOrder: Remove move assignment"

This reverts commit r214260.  Turns out move assignment *is* necessary
for MSVC [1].

[1]: http://bb.pgr.jp/builders/ninja-clang-i686-msc17-R/builds/9631

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@214264 91177308-0d34-0410-b5e6-96231b3b80d8

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