[CppAD] Mac OS limits test failing

[Brad Bell]

There seems to be a problem with the MAC OS gcc compiler implementation 
of complex division. See
     http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56542

This is causing the complex cases for the function
     bool limits(void)
in the file
     test_more/limits.cpp
to fail. A web version of this file can be viewed at
https://projects.coin-or.org/CppAD/browser/trunk/test_more/limits.cpp

If you run into this problem, you could comment out the complex cases in 
the function
     bool limits(void)
in order to test the other cases.