ENHANCED: Better reporting for time/1.

[triska]

This addresses #378.

[triska]

I think I finally solved this.

Example:

?- time(member(X, "abc")).
%@    % CPU time: 0.005 seconds
%@    X = a
%@ ;  % CPU time: 0.000 seconds
%@    X = b
%@ ;  % CPU time: 0.000 seconds
%@    X = c
%@ ;  % CPU time: 0.000 seconds
%@    false.

[triska]

There is one remaining issue: If time/1 calls are nested, the system loops unexpectedly on the second invocation. For example:

?- time(time(true)).
%@    % CPU time: 0.007 seconds
%@    % CPU time: 0.021 seconds
%@    true.

And it loops the second time we execute it. I have filed a separate issue, #1123 for this specific phenomenon, with a small snippet that exhibits the same issue.