sync: unpublish LocksHeld() which is used only in sync.cpp

src/sync.cpp

@@ -246,7 +246,7 @@ void LeaveCritical()
     pop_lock();
 }
 
-std::string LocksHeld()
+static std::string LocksHeld()
 {
     LockData& lockdata = GetLockData();
     std::lock_guard<std::mutex> lock(lockdata.dd_mutex);

src/sync.h

@@ -57,7 +57,6 @@ template <typename MutexType>
 void EnterCritical(const char* pszName, const char* pszFile, int nLine, MutexType* cs, bool fTry = false);
 void LeaveCritical();
 void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line);
-std::string LocksHeld();
 template <typename MutexType>
 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) EXCLUSIVE_LOCKS_REQUIRED(cs);
 template <typename MutexType>