gmond compilation fix for 3.7 branch

Hi,

when trying to compile the 3.7 version of Ganglia on Debian Squeeze (6.0), I'm experiencing troubles with making of gmond. Problem is in gengetopt_args_info structure from gmond/cmdline.h. Attached patch is fixing this issue/typo in the structure variable name.

```
$ ./bootstrap
[...]

$ ./configure --prefix=/usr --with-gmetad --disable-php \
 --enable-perl --enable-status \
 --enable-python --with-riemann
[...]
```

```
$ make
[...]
gmond.c: In function ‘socket_send’:
gmond.c:267: error: ‘struct gengetopt_args_info’ has no member named ‘gzip_output_flag’
gmond.c: In function ‘process_tcp_accept_channel’:
gmond.c:2050: warning: passing argument 4 of ‘apr_socket_data_set’ from incompatible pointer type
/usr/include/apr-1.0/apr_network_io.h:467: note: expected ‘apr_status_t (*)(void *)’ but argument is of type ‘void (*)(struct z_stream *)’
make[3]: *** [gmond.o] Error 1
```

R.