[Ipopt] Upgrade to C++ version

[Sundar R]

Hello,

We have Ipopt 2.2.1 (Fortran based) and we would like to move a newer version.
1) What are the crucial differences between the C++ and Fortran versions?
2) What are some key reasons to  upgrade?
3) Does the C++ version have quasi-Newton strategies implemented for
Hessian approximation?
    I think the answer is yes, but the FAQ (outdated?) found at
https://projects.coin-or.org/Ipopt/wiki/FAQ says it is slated for
development. Could someone clarify and point me to the latest FAQ?
4) Is Complementarity Handling by constraint relaxation implemented in C++?
  This is important for my work.  If yes, could you please point me to
an example (preferably C++) that shows how to use Ipopt to solve a
model with complementarities?
5) Is there a list of known issues with Ipopt? How frequent are the
bug fixes & releases?

Thanks
Sundar