Merge r1457471, r1457504, r1462266, r1468581 from trunk:

mod_auth_basic: Add a generic mechanism to fake basic authentication
using the ap_expr parser. This allows the administrator to construct
their own username and password for basic authentication based on their
needs. Alternative fix for PR52616.


Remove the Authorization header should either the username or the password
resolve to an empty string.


* Inherit providers during merging

mod_auth_basic: Allow AuthBasicFake to be switched off for an URL space.

Submitted by: minfrin, rpluem, minfrin
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1502199 13f79535-47bb-0310-9956-ffa450edef68