Add an option to display the changes instead of the added and removed characters

When listing the removed and added characters, it is a bit hard
to see in the report that some characters which are removed from
a width are added again with another width. For example:

removed: 0x302a : 0 eaw=W category=Mn bidi=NSM name=IDEOGRAPHIC LEVEL TONE MARK

added: 0x302a : 2 eaw=W category=Mn bidi=NSM name=IDEOGRAPHIC LEVEL TONE MARK

It is easier to see the  changes  by listing them like this:

changed width: 0x302a : 0->2 eaw=W category=Mn bidi=NSM name=IDEOGRAPHIC LEVEL TONE MARK

This can be done using the “-c” option now.