* easy proposals to synch 2.4.x and trunk

  - Use apr_file_printf(... "%pm"...) instead of explicit call to apr_strerror
  - remove unused variables
  - axe some useless assignments (clang scan-build)
  - Remove useless apr_pstrdup as done for other mod_auth modules in r1026660
  - Remove unused APXS setting from template for generated Makefile


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1553528 13f79535-47bb-0310-9956-ffa450edef68