fix this:

mod_auth_digest.c: In function ‘set_shmem_size’:
mod_auth_digest.c:681: warning: format ‘%ld’ expects type ‘long int’, but argument 7 has type ‘apr_size_t’


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@886213 13f79535-47bb-0310-9956-ffa450edef68