name an array function (follow up from guile-user)

See https://lists.gnu.org/archive/html/guile-user/2016-12/msg00014.html. This is just renaming, but the doc could use a review. Thanks.

[PATCH] Final names for new array functions

From: Daniel Llorens Globally rename (array-from* -> array-slice), (array-from -> array-cell-ref), (array-amend! -> array-cell-set!), (array-for-each-cell -> array-slice-for-each). --- doc/ref/api-data.texi | 112 +++- libguile/array-map.c