Changed "auto_flush" to "force_flush" to better represent the meaning

include/spdlog/details/file_helper.h

@@ -48,9 +48,9 @@ public:
     const int open_tries = 5;
     const int open_interval = 10;
 
-    explicit file_helper(bool auto_flush):
+    explicit file_helper(bool force_flush):
         _fd(nullptr),
-        _auto_flush(auto_flush)
+        _force_flush(force_flush)
     {}
 
     file_helper(const file_helper&) = delete;
@@ -104,7 +104,7 @@ public:
         if(std::fwrite(data, 1, size, _fd) != size)
             throw spdlog_ex("Failed writing to file " + _filename);
 
-        if(_auto_flush)
+        if(_force_flush)
             std::fflush(_fd);
 
     }
@@ -131,7 +131,7 @@ public:
 private:
     FILE* _fd;
     std::string _filename;
-    bool _auto_flush;
+    bool _force_flush;
 
 
 };