Added thread-safety to thumbnail request system.

Marked symbol requests as not being thread-safe.
Added icon to symbol editor
Made *.* actually register on *



git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@407 0fc631ac-6414-0410-93d0-97cfa31319b6

src/gui/control/image_card_list.cpp

@@ -84,6 +84,8 @@ class CardThumbnailRequest : public ThumbnailRequest {
 			parent->Refresh(false);
 		}
 	}
+
+	virtual bool threadSafe() const {return true;}
   private:
 	String filename;
 };