Merge r1408958, r1408961, r1409170 from trunk:

mod_session_dbd: fix a segmentation fault in the function dbd_remove.
The segmentation fault is caused by an uninitialized function pointer session_dbd_acquire_fn.
PR 53452

formatting: space vs tab

Axed C++ comments.

Submitted by: jailletc36, fuankg
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1416583 13f79535-47bb-0310-9956-ffa450edef68