Add support for `do` statement bodies that are not block statements

Added support for do-statement bodies that are not block statements in the same way that we can already do with e.g. if or while statements.

The new functionality will obey the `curly` option and allows the statement body to appear on the same line or the following line (in which case existing indentation rules will apply).

Here is a [Stack Overflow question](http://stackoverflow.com/questions/16411162/is-it-possible-and-reasonable-to-convince-jshint-to-accept-a-single-line-do-lo) which prompted this patch.