[eclipse-pmc] API request: setting a view's busy state

[Boris Bokowski <Boris_Bokowski@xxxxxxxxxx>]

Platform/UI would like to request a new method
IWorkbenchSiteProgressService.showBusy(boolean).  This will allow views to
control their busy indication explicitly (shown by italic font in the view
tab).

GOALS/BENEFITS:
- allows views that update asynchronously, but don't use jobs, to be
consistent with our UI metaphor for being busy

CORRESPONDING BUG(S):

https://bugs.eclipse.org/bugs/show_bug.cgi?id=179089

RISKS:

No risk, all API additions.

PERFORMANCE IMPACTS:

No performance impact