• Added OptionsList::UnsetValue() to remove an option setting.
• Added missing translation of some Ipopt status codes into AMPL solve result codes.
• If using the MPI-parallel version of MUMPS: Moved calls to MPI_Init()/MPI_Finalize() in MUMPS interface into global constructor/destructor of Ipopt library (if building with GCC/clang). Use configure flag --disable-mpiinit to disable. [#500]