SE-0496: `@inline(always)` Attribute

[Douglas_Gregor]

@ricketson

The proposal mentions @_alwaysEmitIntoClient, but only in passing in one of the code examples when discussing interactions with @inlinable. Even though @_alwaysEmitIntoClient is an underscore’d attribute, can the proposal add more clarity about how we should expect this new attribute to interact with it?

There is a separate pitch thread about formalizing @_alwaysEmitIntoClient, which goes into depth on the relationship.

Doug