Allow actually setting cursor colors on Haiku

Allow actually setting cursor colors on Haiku

* src/haiku_support.cc (be_create_pixmap_cursor): New function.
* src/haiku_support.h: Update prototypes.

* src/haikufns.c (haiku_create_frame): Change default cursor
color to "font-color".
(haiku_create_tip_frame): Likewise.

(struct user_cursor_bitmap_info): New struct.
(cursor_bitmaps): New list of bitmaps corresponding to cursors.
(haiku_create_colored_cursor): New function.
(haiku_free_custom_cursors): Set current cursor to the default
cursor before freeing the original value.
(haiku_set_mouse_color): Actually recolor cursors based on
built-in bitmaps.

* src/haikuterm.c (haiku_defined_color): Clean up coding style.