Simplify visual comparison

[pjljvandelaar]

When the actual and expected string differ, the following message is produced:

aunit/include/aunit/framework/aunit-assertions.adb

Line 109 in 552a240

Message & " - got '" & Actual & "', expecting '" & Expected & "'",

Could this message be split over multiple lines such that a user can more easily see the difference.
E.g.

got      - '1234567890ABCDEF'
expected - '123456789ABCDEF'