Add loading history message on initial MAM request

This prevents scrolling to top and initiating another MAM request while
still fetching the initial one.
Also free timestamp object in database.c

src/ui/window.h

@@ -77,6 +77,7 @@ void win_print_http_transfer(ProfWin* window, const char* const message, char* u
 
 void win_newline(ProfWin* window);
 void win_redraw(ProfWin* window);
+void win_print_loading_history(ProfWin* window);
 int win_roster_cols(void);
 int win_occpuants_cols(void);
 void win_sub_print(WINDOW* win, char* msg, gboolean newline, gboolean wrap, int indent);