[h323plus] OpenMCU now supports up to 16CIF mixer

To all

OpenMCU now supports either CIF, 4CIF or 16CIF video mixer. This means if endpoints are about to support HD and large frame sizes then they can send and receive at those frame sizes with the MCU with H.263.

By default it is still CIF but you can change the size by altering the frameSize variable in the constructor of the OpenMCU class.

Simon