bitchx: new formula; BitchX IRC client.

The popular BitchX IRC client:

* https://github.com/BitchX/BitchX1.2#readme
* https://github.com/BitchX/BitchX1.2/wiki
* http://www.bitchx.ca/
* http://en.wikipedia.org/wiki/Bitchx

Previously proposed in mxcl/homebrew#1139 and mxcl/homebrew#10246,
and mentioned in mxcl/homebrew#5549, however a stable version was not
available at those times.

Since then, BitchX 1.2-final has been released.

It builds and runs without any patches or other complications.

While irssi is more popular for new users, BitchX has had a strong
following for over a decade. From the README:

> As of 12/31/2012 we are releasing BitchX-1.2-final.
> 18 years of BitchX and we're not nearly done yet.

----

No non-system dependencies:

```
$ otool -L /usr/local/bin/BitchX
/usr/local/bin/BitchX:
  /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 169.3.0)
  /usr/lib/libncurses.5.4.dylib (compatibility version 5.4.0, current version 5.4.0)
  /usr/lib/libssl.0.9.8.dylib (compatibility version 0.9.8, current version 47.0.0)
  /usr/lib/libcrypto.0.9.8.dylib (compatibility version 0.9.8, current version 47.0.0)
  /usr/lib/libresolv.9.dylib (compatibility version 1.0.0, current version 1.0.0)
```

Audit is good:

```
$ brew audit bitchx && echo ok
ok
```

Install is good:

```
$ brew install bitchx
==> Downloading http://bitchx.ca/BitchX-1.2-final.tar.gz
==> ./configure --prefix=/usr/local/Cellar/bitchx/1.2 --with-ssl --with-plugins --enable-ipv6
==> make