mat-radio-button and mat-checkbox don't line wrap

#### Bug, feature request, or proposal:

Proposal: change `` or `` to line-wrap its contents by default or add an option.

#### What is the expected behavior?

I can put a text into a `` or `` that is longer than what fits into the viewport.

#### What is the current behavior?

The content in a or does not line wrap. If you have a lot of text in a it gets cut at the end.

A workaround would be
`{{mylongtext}}`

#### What are the steps to reproduce?

https://stackblitz.com/edit/angular-material2-issue-uaeetd?file=app/app.component.html

#### What is the use-case or motivation for changing an existing behavior?

I have a pretty narrow window and need to put checkboxes and radio buttons in there.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?

I think all of them.

#### Is there anything else we should know?

Commencez par la reproduction StackBlitz liée, en particulier app/app.component.html, et vérifiez l'absence de retour à la ligne pour les contenus longs de mat-radio-button et mat-checkbox dans un viewport étroit. La tâche est terminée lorsque le contenu revient à la ligne par défaut ou via une option documentée, tout en préservant le comportement existant des composants.

Rédigé par le modèle d'indexation à partir du texte de l'issue.