Normal mode 'r' key doesn't work with macron / IM input

In macOS, you can enter macron input using an Option key sequence. E.g. Typing <M-e>, then i should result in "í" being inputted. This works in insert mode, but if you do this in the replace mode (r command in normal mode) it doesn't work. The above key sequence will enter ´, while the i will be ignored.

This can be worked around by disabling "Draw marked text inline" in advanced preferences but is not ideal, and there may be issues with how the replace mode interfaces with other input methods (IM) as well, so investigate and fix that.

Original discussion: https://groups.google.com/forum/#!topic/vim_mac/9JuxOuUFqgg

Commencez par reproduire la séquence de touches Option de macOS signalée en mode remplacement (r) et comparez-la au mode insertion, en vous concentrant sur la gestion du texte marqué et de la méthode de saisie. C’est terminé lorsque la séquence produit le caractère accentué tout en remplaçant un caractère, sans désactiver « Draw marked text inline. ».