support Apache2.4

In Apache2.4, Following changes make building mod_dosdetector failed.

* ap_default_type is removed
* r->connection->remote_(ip|addr) is renamed to r->connection->client_(ip|addr)

```zsh
$ make
/usr/local/apache2/bin/apxs -c    mod_dosdetector.c
/usr/share/apr-1.0/build/libtool --silent --mode=compile x86_64-linux-gnu-gcc -std=gnu99 -prefer-pic   -D_REENTRANT -D_GNU_SOURCE -pthread -I/usr/local/apache2/include  -I/usr/include/apr-1.0   -I/usr/include/apr-1.0 -I/usr/include  -c -o mod_dosdetector.lo mod_dosdetector.c && touch mod_dosdetector.slo
mod_dosdetector.c: In function ‘create_shm’:
mod_dosdetector.c:144:5: warning: format ‘%d’ expects argument of type ‘int’, but argument 9 has type ‘size_t’ [-Wformat]
mod_dosdetector.c: In function ‘dosdetector_handler’:
mod_dosdetector.c:263:5: warning: implicit declaration of function ‘ap_default_type’ [-Wimplicit-function-declaration]
mod_dosdetector.c:263:37: warning: assignment makes pointer from integer without a cast [enabled by default]
mod_dosdetector.c:274:26: error: ‘conn_rec’ has no member named ‘remote_ip’
mod_dosdetector.c:288:23: error: ‘conn_rec’ has no member named ‘remote_addr’
$
```

# Note

|My Environment|Version|
|---------|-----------|
|Compiler|GCC 4.7.2|
|OS|Linux Mint 14(nadia) 64bit kernel-release is 3.5.0-27-generic|
|Apache|2.4.4|