[eclipse-pmc] API Request - add API to JFace ControlDecoration

[Susan M Franklin <susan_franklin@xxxxxxxxxx>]

Please see 
https://bugs.eclipse.org/bugs/show_bug.cgi?id=172294

The request is to add a constructor to ControlDecoration which introduces
a new Composite parameter. 
This allows clients to specify which on which particular composite the
decoration should be rendered, so that they can better control dynamic
hide/show behavior, clipping issues, etc.   
The default behavior remains the same. 

There will be an additional API request
to add function to ControlDecoration, but this will be addressed separately.

thanks, 
Susan Franklin McCourt