[eclipse-pmc] API Request: adding task name propagation and convenience

[Oleg Besedin <obesedin@xxxxxxxxxx>]

Users of the SubMonitor class (added
in the December 2006 into org.eclipse.equinox.common) asked for the following
non-breaking improvements: 

GOALS/BENEFITS:
- a set of flags to explicitly control
propagation of the task name through the chain of progress monitors
- a method that creates child monitor
using one of those flags
- a new factory method to avoid passing
bogus number of ticks to the monitor when number of ticks is unknown

CORRESPONDING BUG:
- SubMonitor#convert doesn't always
set task name
        https://bugs.eclipse.org/bugs/show_bug.cgi?id=174040
- Add a 1-argument convert(...) method
to SubMonitor
        https://bugs.eclipse.org/bugs/show_bug.cgi?id=174539

RISKS:
- no known risks

PERFORMANCE IMPACTS:
- no impact

Thanks,
Oleg