swift234

Revert "Fix two problems with implicit conversions: - rdar://problem/16776273, wherein conversions between nil and .None were permitted due to an implicit conversion between nil and COpaquePointer. - rdar://problem/16877526, where we needed to add new equality overloads to handle conversions between nil and .None given the supression of user conversions. (Thanks to Ted for the overloads and test.)"

This reverts commit r18473.

Swift SVN r18477