iOS: fix app id in path, pen pressure filtering on Line

src/asset.cpp

@@ -31,7 +31,7 @@ bool Asset::exist(std::string path)
     }
     else
     {
-        std::ifstream f(path);
+        std::ifstream f(path, std::ios::binary);
         return f.is_open();
     }
     return false; // useless return for the stupid xcode