remove use of Mutex in favour of std::{,recursive_}mutex

This is a pretty straightforward first pass over removing a number of uses of
Mutex in favor of std::mutex or std::recursive_mutex. The problem is that there
are interfaces which take Mutex::Locker & to lock internal locks. This patch
cleans up most of the easy cases. The only non-trivial change is in
CommandObjectTarget.cpp where a Mutex::Locker was split into two.

llvm-svn: 269877

lldb/source/Target/Process.cpp

@@ -1795,7 +1795,7 @@ Process::SetPrivateState (StateType new_state)
         log->Printf("Process::SetPrivateState (%s)", StateAsCString(new_state));
 
     Mutex::Locker thread_locker(m_thread_list.GetMutex());
-    Mutex::Locker locker(m_private_state.GetMutex());
+    std::lock_guard<std::recursive_mutex> guard(m_private_state.GetMutex());
 
     const StateType old_state = m_private_state.GetValueNoLock ();
     state_changed = old_state != new_state;