Keeping backported CHANGES in trunk CHANGES?

[Rainer Jung]

In trunk we do now have a 2.5 CHANGES file, ie. the file contains 
entries for 2.5.0-alpha and the entries above those under the 2.5.1 heading.

I think we should add entries under 2.5.1 even if things get likely 
backported and such items should no longer be removed when being 
backported. Before 2.5.0-alpha, that was just a candidate CHANGES file 
for the things not in 2.4.x, but now it should also document the changes 
after 2.5.0-alpha. Similar to how I think it was done while switching 
from 2.2 to 2.3/2.4.

Regards,

Rainer