Merge r1653941, r1653978, r1656225, r1686853, r1686856 from trunk:

Merge r1653941, r1653978, r1656225, r1686853, r1686856 from trunk:

mod_alias: Introduce expression parser support for Alias, ScriptAlias
and Redirect.

Use unsigned bit fields.

mod_alias: follow up to r1653941.
Fill empty APLOGNO().

mod_alias: follow up to r1653941.
Limit Redirect expressions to directory (Location) context
and redirect statuses (implicit or explicit).

mod_alias: follow up to r1686853.
Factorize code (no functional change).
Submitted by: minfrin, ylavic, ylavic, ylavic
Reviewed/backported by: jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1731081 13f79535-47bb-0310-9956-ffa450edef68