Port some constructors to pass-by-value using C++11 move semantics

Performed using modernize-pass-by-value from clang-tidy.

Manual intervention was needed to fix an issue in MacroValue.hh.
Also replace std::move by move, since we import the std namespace.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-pass-by-value.html