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
diff --git a/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.h b/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.h
index a1d255c..888e2a9 100644
--- a/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.h
+++ b/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.h
@@ -13,8 +13,9 @@
 // C Includes
 
 // C++ Includes
-#include <set>
+#include <mutex>
 #include <queue>
+#include <set>
 
 // Other libraries and framework includes
 #include "lldb/Target/Process.h"
@@ -212,7 +213,7 @@
     lldb_private::Module *m_module;
 
     /// Message queue notifying this instance of inferior process state changes.
-    lldb_private::Mutex m_message_mutex;
+    std::recursive_mutex m_message_mutex;
     std::queue<ProcessMessage> m_message_queue;
 
     /// Drive any exit events to completion.