Implement ProcessMonitor::Kill for Linux

On FreeBSD ptrace(PT_KILL) is used to terminate the traced process
(as if PT_CONTINUE had been used with SIGKILL as the signal to be
delivered), and is the desired behaviour for ProcessPOSIX::DoDestroy.

On Linux, after ptrace(PTRACE_KILL) the traced process still exists
and can be interrogated.  It is only upon resume that it exits as though
it received SIGKILL.

As the Linux PTRACE_KILL behaviour is not used by LLDB, rename
BringProcessIntoLimbo to Kill, and change the implementation to simply
call kill() instead of using ptrace.

Thanks to Todd F for testing (Ubuntu 12.04, gcc 4.8.2).

Sponsored by: DARPA, AFRL
Differential Revision: http://llvm-reviews.chandlerc.com/D3159

llvm-svn: 205337
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index 3dec6de..198a1eb 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -904,31 +904,6 @@
 }
 
 //------------------------------------------------------------------------------
-/// @class KillOperation
-/// @brief Implements ProcessMonitor::BringProcessIntoLimbo.
-class KillOperation : public Operation
-{
-public:
-    KillOperation(bool &result) : m_result(result) { }
-
-    void Execute(ProcessMonitor *monitor);
-
-private:
-    bool &m_result;
-};
-
-void
-KillOperation::Execute(ProcessMonitor *monitor)
-{
-    lldb::pid_t pid = monitor->GetPID();
-
-    if (PTRACE(PTRACE_KILL, pid, NULL, NULL, 0))
-        m_result = false;
-    else
-        m_result = true;
-}
-
-//------------------------------------------------------------------------------
 /// @class DetachOperation
 /// @brief Implements ProcessMonitor::Detach.
 class DetachOperation : public Operation
@@ -2229,12 +2204,9 @@
 }
 
 bool
-ProcessMonitor::BringProcessIntoLimbo()
+ProcessMonitor::Kill()
 {
-    bool result;
-    KillOperation op(result);
-    DoOperation(&op);
-    return result;
+    return kill(GetPID(), SIGKILL) == 0;
 }
 
 bool