There are two separate recursion control obstacks in cp-valprint.c, both 
originally incorrectly using obstack_next_free().  I fixed one of those 
in the patch for pr9167, but the other one would have collided with the 
patch for pr10687.  Here is the fix for the second instance.  (No new 
testcases are required--the existing t/cs for pr9067, pr9167, and 
pr10687 test the code in this patch.)

Chris