Clean up lots of #ifdef'd out code in PGTK files

Clean up lots of #ifdef'd out code in PGTK files

Most of them are either relics from X or from the NS code
pgtkfns.c was copied from whole.

* src/pgtkfns.c (x_icon):
(pgtk_set_scroll_bar_foreground):
(pgtk_set_scroll_bar_background):
(Fx_create_frame):
(pgtk_window_is_ancestor):
(x_create_tip_frame):
* src/pgtkselect.c (syms_of_pgtkselect):
* src/pgtkterm.c (pgtk_iconify_frame):
(x_set_frame_alpha):
(button_event): Remove defined out code that cannot make sense.

* src/pgtkmenu.c (show_help_event): Remove ifdef'd out code and
reword comment.