swift234

SIL: "Thicken" function refs when necessary.

Swift doesn't yet type-check function thinness, so variables, arguments, and return values are always thick. When we store, pass as argument, or return a function value that SIL tracks as thin, emit a new 'thin_to_thick_function' instruction to represent converting the type to the thick type and adding a null context pointer.

Swift SVN r4470