swift234

Closures and local functions only capture generic parameters if necessary

The CaptureInfo computed by Sema now records if the body of the
function uses any generic parameters from the outer context.
SIL type lowering only adds a generic signature if this is the
case, instead of unconditionally.

This might yield a marginal performance improvement in some cases,
but more interestingly will allow @convention(c) conversions from
generic context.

Swift SVN r32161