Make CImageLoaderJPG thread safe. Thanks @ Edoardo Lolletti for report and patch (patch #324)

Replace a static variable which was used in error-reporting but wasn't thread-safe.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6220 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CImageLoaderJPG.h

@@ -100,9 +100,6 @@ private:
 	data has been read. Often a no-op. */
 	static void term_source (j_decompress_ptr cinfo);
 
-	// Copy filename to have it around for error-messages
-	static io::path Filename;
-
 	#endif // _IRR_COMPILE_WITH_LIBJPEG_
 };