Lessons from trying to checkpoint Apache

This includes patches that add warnings/comments about some of the things that users need to be wary of when testing their applications with DMTCP. We faced these problems when testing DMTCP with Apache-2.2.
Commenting it out is good for now.

For future, we can simply disable the terminal plugin if running with apache.  To do that, we can create a simple apache plugin that takes care of it.