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

Empieza reproduciendo la secuencia de teclas Option de macOS reportada en el modo de reemplazo (r) y compárala con el modo de inserción, centrándote en el manejo del texto marcado y del método de entrada. Se considera terminado cuando la secuencia produce el carácter acentuado al reemplazar un carácter, sin desactivar “Draw marked text inline.”