make member function const

Apply clang-tidy's readability-make-member-function-const fixit.

Author: purpleKarrot

include/mp/proxy-io.h

@@ -172,7 +172,7 @@ class EventLoop
     void addClient(std::unique_lock<std::mutex>& lock);
     bool removeClient(std::unique_lock<std::mutex>& lock);
     //! Check if loop should exit.
-    bool done(std::unique_lock<std::mutex>& lock);
+    bool done(std::unique_lock<std::mutex>& lock) const;
 
     Logger log()
     {

src/mp/proxy.cpp

@@ -277,7 +277,7 @@ void EventLoop::startAsyncThread(std::unique_lock<std::mutex>& lock)
     }
 }
 
-bool EventLoop::done(std::unique_lock<std::mutex>& lock)
+bool EventLoop::done(std::unique_lock<std::mutex>& lock) const
 {
     assert(m_num_clients >= 0);
     assert(lock.owns_lock());