Replace arrays for point hint data with red-black trees.

Replace arrays for point hint data with red-black trees.

This enormously reduces the needed amount of allocated memory.  It also
avoids allocation errors due to overflow in the number of bytes to be
allocated.

The used red-black tree implementation (in file `llrb.h') was written by
William Ahern <william@25thandClement.com>; I've downloaded version
2013-09-25 from

  http://25thandclement.com/~william/projects/llrb.h.html