Simplify Haiku cursor management code

Simplify Haiku cursor management code

* src/haiku_support.cc (BCursor_create_default)
(BCursor_create_modeline, BCursor_from_id, BCursor_create_i_beam)
(BCursor_create_progress_cursor, BCursor_create_grab)
(BCursor_delete): Delete specialized cursor creation functions.
(be_delete_cursor, be_create_cursor_from_id): New functions.
(BView_set_view_cursor): Fix coding style.
* src/haiku_support.h (enum haiku_cursor): Add all cursor IDs.
* src/haikufns.c (haiku_free_custom_cursors):
(haiku_set_mouse_color):
* src/haikuterm.c (haiku_term_init): Adjust accordingly.