Now that fmt plays nice with gcc let's actually use it: replace std::to_string, boost lexical_cast and a couple miscellaneous llformats with fmt. (Alchemy sync-ish)

indra/llui/llscrolllistctrl.cpp

@@ -3201,7 +3201,7 @@ LLScrollListItem* LLScrollListCtrl::addRow(LLScrollListItem *new_item, const LLS
 		// empty columns strings index by ordinal
 		if (column.empty())
 		{
-			column = llformat("%d", col_index);
+			column = fmt::to_string(col_index);
 		}
 
 		LLScrollListColumn* columnp = getColumn(column);