Avoid insensitive expressions "Child aborted", "Child killed", and "Child terminated" in error messages
Problem
The CTest process routine refers to a test subprocess as "child", and reports "Child aborted", "Child killed", or "Child terminated" when given certain signals from said process. Although "child" seems a usual term for referring to a spawned subprocess, combining it with "aborted" or "killed" leads to rather unpleasant associations. This goes especially for persons who might have experienced such a thing or lost their own child.
Proposal
Rename "Child" to "Subprocess" in error messages defined in CTest/cmProcess.cxx
and kwsys/ProcessUNIX.c
Since "child" is a rather common term and occurs many times throughout the code, I'm not asking to refactor everything. Only the part users usually interact with. However, I also think that comments like this one and the following should eventually be refactored.