For PR351: * Allow the ExecuteAndWait to return negative values if a signal is   detected as the reason for the child termination. This is needed to   support bugpoint detecting bad things in its child processes.
For PR351:
* Allow the ExecuteAndWait to return negative values if a signal is
  detected as the reason for the child termination. This is needed to
  support bugpoint detecting bad things in its child processes.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@24960 91177308-0d34-0410-b5e6-96231b3b80d8

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