Part of #6993. Moved a bunch of uses of Ident to Name
Improve code in the intro.

All these stars aren't needed anymore.
auto merge of #18253 : steveklabnik/rust/small_doc_fixes, r=huonw

All these stars aren't needed anymore.
auto merge of #17683 : gereeter/rust/ident-to-name, r=pcwalton

This does a large chunk of #6993. It is based on top of #17654.
Add a lint for not using field pattern shorthands

Closes #17792.