Don't set document text as changed when file on disk is newer

Setting the document text as changed makes it too easy to accidentally
overwrite the file - e.g. when closing you're reminded to save it.
It also makes it slower to close documents you no longer want open.
Setting text as changed is still done if the user cancels the warning.
Set status id to STATUS_DISK_CHANGED when protecting document
Merge pull request #326 from ntrel/reload-modified

Don't set document text as changed when file on disk is newer