[wtp-releng] Source Editing related re-spin for 3.1 M3

[Nitin Dahyabhai <nitind@xxxxxxxxxx>]

The Dali team uncovered a regression
in some of their function due to a change in SSE UI's handling of background
updates to the source editor's contents.  Although it still looks
to me like we're calling the right methods, this would affect anyone doing
a background update and not just Dali functionality.  To be on the
safe side, I'm rolling back the earlier changes to the org.eclipse.wst.sse.ui.EditorExecutionContext
class.  This shouldn't cause anyone to need to retest, apart from
the Dali team, whom I would like to verify bug 253954
when the respin is ready.

Sorry for the delay of the milestone
build.

Regards,
---
Nitin Dahyabhai
Eclipse WTP Source Editing
IBM Rational