identify classes to use mpool based allocation

[ichthyo]

This is a QA ticket for later

Indeed we need a more clear understanding of the actual inner workings before we can consider to target this ticket. Blindly inserting custom operator new into a ton of classes wouldn't be helpful (and might be a dangerous undertaking btw). Instead, we should identify which classes are

• small allocations
• indeed heap allocated most of the time
• created and deleted in great numbers

the MObject hierarchy would be a good candidate, to give an example.

[ichthyo]

Just for sake of clarity: the most important allocation problem within proc layer is already covered by AllocationCluster (which in turn is expected to use mpool as a backend (see #101). Thus this ticket is not about solving an urgent performance problem, but for improving the overall situation (thus the lesser priority)