Fixed compile error with mingw

src/BufferedFile.cc

@@ -50,7 +50,7 @@ const char BufferedFile::APPEND[] = "ab";
 BufferedFile::BufferedFile(const char* filename, const char* mode)
   :
 #ifdef __MINGW32__
-  fp_(a2fopen(utf8ToWChar(filename).c_str(), utf8ToWChar(mode).c_str)),
+  fp_(a2fopen(utf8ToWChar(filename).c_str(), utf8ToWChar(mode).c_str())),
 #else // !__MINGW32__
   fp_(a2fopen(filename, mode)),
 #endif // !__MINGW32__