Corrected "Ownership":
- [`Variable bindings`] link was not processed properly.
- Changed the paragraph about move semantics with two vectors, because it was confusing.
- Removed "So it may not be as inefficient as it initially seems", because there is nothing that seems inefficient in copying pointers only.
- Other text corrections.
Fixed copied-and-pasted text mistakes.
Revised the paragraph about moving a vector (taking into account suggestions by echochamber).
Fixed markdown.
Fixes requested by steveklabnik.
Brought back a sentence about supposed inefficiency.
