Performance hit with --enable-atomic-refcount

[Rik]

6/6/14

All,

>From the previous benchmarking, there was a doubling in execution time from
3.8.1 to the gui-release branch for a nested for loop.  It turns out that
this doubling is 100% correlated with using the --enable-atomic-refcount
option to configure.  I built the gui-release branch with this feature
disabled and the results are then equivalent to the 3.8.1 release.  It
seems like we need to explore a different solution than this configure
option so that we can both use Qt graphics and have reasonable performance.

Cheers,
Rik