swift234

Stop giving local types private linkage; the debugger may still access them.

Instead, just fall through to the normal public/internal/private switch
added in the previous commit. Local declarations are always private.

Make sure we emit all local declarations by using the list in the SourceFile,
rather than walking the AST (which missed a few cases and was less efficient
anyway).

As an exception, declarations without accessibility at all still get private
linkage. These are things like local variables that don't get accessed by
symbol, even when using the debugger.

rdar://problem/19623016

Swift SVN r24839