The generic bounds utility used an incorrect initial value. The value
cannot be zero-initialized, because that breaks the case where all
values are greater than zero.
Finding the greatest and/or smallest element in an array is a common
need. This commit refactors the point cloud bounds code added in
6d7dbdbb44f379682 to a more general header in blenlib.
This will allow reusing the algorithm for curves without duplicating it.
Differential Revision: https://developer.blender.org/D14053
