Make IDocument::fileName a member with setter.

Instead of requiring subclasses to implement a method.
Also renames IDocument::rename to IDocument::setFileName,
since it doesn't really rename any files or such.

Change-Id: I1344025c24d2f74a6a983e04fb0a5245f1f37aad
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/diffeditor/diffeditorfile.cpp

@@ -41,20 +41,6 @@ DiffEditorFile::DiffEditorFile(const QString &mimeType, QObject *parent) :
 {
 }
 
-void DiffEditorFile::rename(const QString &newName)
-{
-    Q_UNUSED(newName);
-    return;
-}
-
-void DiffEditorFile::setFileName(const QString &name)
-{
-    if (m_fileName == name)
-        return;
-    m_fileName = name;
-    emit changed();
-}
-
 void DiffEditorFile::setModified(bool modified)
 {
     if (m_modified == modified)