Merge r1551611, r1783765, r1788996, r1788998, r1789000, r1795651 from trunk:

Log a warning when the LDAP authn provider is configured but an AuthLDAPURL 
isn't -- IOW, avoid silently skipping a misconfigured [or buggy?] LDAP provider.



Follow up to r1772919: update APLOGNO().

Save a few cycles.
'apr_pstrcatv' can compute the length of the new string for us.

Improve indentation

Group bit field values in order to save some memory.

Add an explicit NULL to initialise a field in an authn_provider structure, as done in all other places.  PR 60636
Submitted by: covener, ylavic, jailletc36, jailletc36, jailletc36, jailletc36
Reviewed by: jailletc36, jim, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1800268 13f79535-47bb-0310-9956-ffa450edef68