When a partial equivalency record is merged, the existing members are 
updated.  The resulting PE size for each member should be the minimum of 
what it was, and the size of the object it is now based on.  The code 
was simply setting it to the new size, which sometimes overwrote the 
correct result.

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  Pushed.

Andrew