Use g_slice_ functions directly and drop macros.

thunar/thunar-browser.c

thunar/thunar-clipboard-manager.c

thunar/thunar-exec.c

thunar/thunar-launcher.c

thunar/thunar-private.h

thunar/thunar-renamer-model.c

thunar/thunar-renamer-pair.c

thunar/thunar-shortcuts-model.c

thunar/thunar-thumbnailer.c

thunar/thunar-transfer-job.c

thunar/thunar-tree-model.c

thunar/thunar-tree-view.c