Remove Logger_File mutex

This is not providing protection for all of the logging, so it gives a
false sense of security. We're also not making use of this as we have
barely any threading.

The exception is the WinVNC code, which is very thread heavy. But it is
unmaintained and will not be a blocker for this.

common/rfb/Logger_file.cxx

@@ -26,8 +26,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <os/Mutex.h>
-
 #include <rfb/Logger_file.h>
 
 using namespace rfb;
@@ -37,19 +35,15 @@ Logger_File::Logger_File(const char* loggerName)
     m_lastLogTime(0)
 {
   m_filename[0] = '\0';
-  mutex = new os::Mutex();
 }
 
 Logger_File::~Logger_File()
 {
   closeFile();
-  delete mutex;
 }
 
 void Logger_File::write(int /*level*/, const char *logname, const char *message)
 {
-  os::AutoMutex a(mutex);
-
   if (!m_file) {
     if (m_filename[0] == '\0')
       return;

common/rfb/Logger_file.h

@@ -26,8 +26,6 @@
 
 #include <rfb/Logger.h>
 
-namespace os { class Mutex; }
-
 namespace rfb {
 
   class Logger_File : public Logger {
@@ -47,7 +45,6 @@ namespace rfb {
     char m_filename[PATH_MAX];
     FILE* m_file;
     time_t m_lastLogTime;
-    os::Mutex* mutex;
   };
 
   bool initFileLogger(const char* filename);