Merge r1713043, r1802305, r1802309 from trunk:

Merge r1713043, r1802305, r1802309 from trunk:

Save a few bytes in conf pool when processing 'Define'.

+ some minor style issues
+ split long lines

Be explicit and safe (const) with the strings stored in ap_server_config_defines.

Follow up to r1713043.

ap_server_config_defines and ap_server_{pre,post}_read_config are arrays of
*const* strings (must not change after being inserted), make it explicit.

Submitted by: jailletc36, ylavic, ylavic
Reviewed by: ylavic, jorton, jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1805223 13f79535-47bb-0310-9956-ffa450edef68