Revert "Remove array_from_ptr function"

This reverts commit ee798d28898ddc1075ecef162bcb54afde658b0d.
Tweak array_from_ptr to accept more type inputs
Add test of array_from_ptr with pointer[T] type
Add pointer[T] support in copy_to_pyobject arrfunc
Merge pull request #127 from mwiebe/arr_from_ptr

Reinstate _lowlevel.array_from_ptr function