fixed for mod_bw when getting an error "undefined symbol: apr_atomic_add"

I download the apache module mod_bw-0.7.gz and compile it with apache2.2.21 on centos44-64.

To compile the package you need to run the following command as root:
# apxs -i -a -c mod_bw.c

That will install the module correctly, but when you add the configuration option to your vhost configs you might get an error "undefined symbol: apr_atomic_add". When that happens, open the file mod_bw.c and change the following:

Before:

/* Compatibility for ARP < 1 */
#if (APR_MAJOR_VERSION < 1)
#define apr_atomic_inc32 apr_atomic_inc
#define apr_atomic_dec32 apr_atomic_dec
#define apr_atomic_add32 apr_atomic_add
#define apr_atomic_cas32 apr_atomic_cas
#define apr_atomic_set32 apr_atomic_set
#endif

AFTER

/* Compatibility for ARP < 1 */
/*
#if (APR_MAJOR_VERSION < 1)
#define apr_atomic_inc32 apr_atomic_inc
#define apr_atomic_dec32 apr_atomic_dec
#define apr_atomic_add32 apr_atomic_add
#define apr_atomic_cas32 apr_atomic_cas
#define apr_atomic_set32 apr_atomic_set
#endif
*/