mod_proxy: Rename dirconn_entry to exclude_entry

Currently they are used for NoProxy, but could be reusable to ProxyBlock.
Rename them to something more generic.
mod_proxy: Match resolved addresses for NoProxy too

We resolve the names using the configuration parsing, thus we already have the
addresses. It could be redundant for NoProxy, but the same code could be used
with ProxyBlock if it did this.
mod_proxy: Split the NoProxy parameter parsing away

It is nice and could be reused by ProxyBlock.
mod_proxy: Share NoProxy parameter parsing and evaluation with ProxyBlock

They do the same task now, so we can remove some duplicate code. They do the
same thing except that ProxyBlock does certain things better -- they support
masked network addresses, thus we can now block subnets.