Vectors should be made shared when required by the use of the copy and not at the point of making the copy itself.

Implemented the non-replacement form of the "dimnames" function, enabled the replacement form, and added tests.

FastR: an implementation of R in Java atop Truffle and Graal. Contributed by Tomas Kalibera, Petr Maj, and Jan Vitek (Purdue University); Christian Humer and Andreas Woess (Johannes Kepler University Linz); Michael Haupt, Mick Jordan, Adam Welc, Christian Wirth, and Thomas Wuerthinger (Oracle Labs).