start piped loggers via the shell, passing through the environment variables

in the httpd process

this requires a new APR feature (APR_SHELLCMD_ENV), just added to apr 1.0-dev


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104019 13f79535-47bb-0310-9956-ffa450edef68