swift234

SIL: Serialize bodies of local functions inside @_transparent functions

A transparent function might be deserialized and inlined into a function
in another module, which would cause problems if the function referenced
local functions.

Previously we would force local functions to have public linkage instead,
which worked, but was not resilient if the body of the transparent
function changed in the module that contained it.

Add a library evolution test ensuring that such a change is resilient
now.

Part of https://bugs.swift.org/browse/SR-267.