Rename thunarx methods *_actions to *_menu_items

docs/reference/thunarx/thunarx-sections.txt

examples/tex-open-terminal/tex-open-terminal.c

plugins/thunar-uca/thunar-uca-provider.c

plugins/thunar-wallpaper/twp-provider.c

thunar/thunar-dnd.c

thunar/thunar-renamer-dialog.c

thunar/thunar-shortcuts-view.c

thunar/thunar-standard-view.c

thunar/thunar-tree-view.c

thunar/thunar-util.c

thunar/thunar-util.h

thunar/thunar-window.c

thunarx/thunarx-menu-item.c

thunarx/thunarx-menu-item.h

thunarx/thunarx-menu-provider.c

thunarx/thunarx-menu-provider.h

thunarx/thunarx-preferences-provider.c

thunarx/thunarx-preferences-provider.h

thunarx/thunarx-renamer.c

thunarx/thunarx-renamer.h