Candidate fix for bug 18592.

This reverts Host.cpp LaunchProcess spawn behavior on FreeBSD to be
like Linux (and unlike OS X) with regards to how default signal
handlers and setup on the spawned process. FreeBSD does not reset
default signal handlers on the spawned process after this change.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@199908 91177308-0d34-0410-b5e6-96231b3b80d8