Merging r182153:

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r182153 | mkopec | 2013-05-17 12:27:47 -0700 (Fri, 17 May 2013) | 5 lines

ProcessMonitor improvements for Linux.
-Remove tracing of fork/vfork until we add support for tracing inferiors' children on Linux.
-Add trace exec option for ptrace so that we don't receive legacy SIGTRAP signals on execve calls.
-Add handling of SIGCHLD sent by kernel (for now, deliver the signal to the inferior).

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llvm-svn: 182517