swift234

Allow capture promotion to work within generic functions.

This is to work around rdar://problem/19230183, where the frontend
generates nested functions / closures with generic signatures if they
appear within a generic function, even if they do not use any generic
types.

We now explicitly check the parameters to the function referenced by the
partial_apply rather than just checking for substitutions or checking
whether it has a generic signature.

Fixes rdar://problem/19169437.

Swift SVN r23887