[wtp-releng] We are rolling back base version used in builds

[David M Williams <david_williams@xxxxxxxxxx>]

It seems there's lots of complications
in the new base. 
For example, see https://bugs.eclipse.org/bugs/show_bug.cgi?id=170831

It'll take some time and effort to work
through that, so we'll revert and 
work on local builds to figure out what
we have to change. 

So, we'll roll back to the M4 level
of Eclipse. 

Teams should still release the ICU4J
change, if you haven't already.