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: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8492)