[NTG-context] counter for MPtoPDF calls [feature request]

Hi Hans, I tested the beta from yesterday and I liked the incremented number behind the MPtoPDF calls (in older versions this was always [1]). I'm currently optimizing some of my graphics for trailtypesetting and the incremented counter was really informative. [..] [MP to PDF] (./testbed-mpgraph.1)This is MetaPost, Version 0.901 (Web2c 7.5.3) (testbed-mpgraph.mp (r:\mp-test.mp) [37] ^^^^ [..] In the current beta this number is completely missing. What was this number for and is it possible to attach the current number of MPtoPDF calls? Greetings, Peter