Explicitly add move constructor/assignment operators.

Explicitly add move constructor/assignment operators.

These are needed due to some obscure rules in the standard
about how std::vector selects between copy and move
constructors, which can cause a conforming implementation
to attempt to select the copy constructor of RuleMatcher,
which will fail since std::unique_ptr<> isn't copyable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298294 91177308-0d34-0410-b5e6-96231b3b80d8