Curly Quote coming from a Copy Paste is transformed into ? after cache is reset

Very often when we copy paste content from (french) web or office documents, apostrophes are curly.

Example: l'Economie numérique sur http://assisesdunumerique.fr/actualites/

When we save and view everything seems normal. However, when the cache is reset and the data read from the database again, the character is lost and transformed to a ?

It seems this character is not supported by iso-8859-1. This problem has not been tested on UTF-8.

The valid character for apostrophes is a straight apostrophe or quote: '

This is a very very annoying bug since it is the most common copy paste issue. There are others like the Euro character.
If we can find a simple fix that would be great.