Configure: untabify indentation

The indentation in the Configure file is currently very strange when
viewed in an editor with a tab width of four spaces, because it has
mixed tab-and-whitespace indentation, which was apparently done with
a tab width of eight spaces.

This commit converts all tabs to spaces using expand(1) with default
    settings. To verify that there are only whitespace changes, use

   git show --ignore-space-change  <this commit>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8512)