Fix default frame name on Haiku

Fix default frame name on Haiku

* src/haikufns.c (haiku_set_background_color)
(haiku_set_cursor_color, haiku_get_pixel, haiku_put_pixel)
(haiku_set_internal_border_width)
(haiku_set_inhibit_double_buffering)
(Fhaiku_mouse_absolute_pixel_position, Fxw_color_defined_p)
(Fxw_color_values, Fx_double_buffered_p)
(Fx_display_backing_store): Clean up coding style.
(haiku_set_name): Use correct default name and don't cons extra
string all the time.

* src/haikuterm.c (haiku_read_socket): Remove unused variable.
(haiku_term_init): Set default name.
(mark_haiku_display): Mark new field.

* src/haikuterm.h (struct haiku_display_info): New field
`default_name'.