Update link to WinPcap installer. Clarify that Wireshark is optional

doc/scapy/installation.rst

@@ -364,7 +364,7 @@ You need the following software packages in order to install Scapy on Windows:
   * `Python <http://www.python.org>`_: `python-2.5.4.msi <http://www.python.org/ftp/python/2.5.4/python-2.5.4.msi>`_. After installation, add ``C:\Python25`` and ``C:\Python25\Scripts`` to your PATH. I'm using Python 2.5. Scapy-win does not work with Python 2.4 or 2.6, because not all third-party extensions on this page are available for them.
   * `Scapy <http://www.secdev.org/projects/scapy/>`_: `latest version from the Mercurial repository <http://scapy.net>`_. Unzip the archive, open a command prompt in that directory and run "python setup.py install".
   * `pywin32 <http://python.net/crew/mhammond/win32/Downloads.html>`_: `pywin32-214.win32-py2.5.exe <http://surfnet.dl.sourceforge.net/sourceforge/pywin32/pywin32-214.win32-py2.5.exe>`_ 
-  * `Wireshark <http://www.wireshark.org/>`_: `Wireshark download page <http://www.wireshark.org/download.html>`_. If you get WinPcap installation errors on Windows 7, please run the installation program in "Vista compatibility" mode. You might want to choose "[x] Start WinPcap service 'NPF' at startup", so that non-privileged users can sniff, especially under Vista and Windows 7.
+  * `WinPcap <http://www.winpcap.org/>`_: `WinPcap_4_1_1.exe <http://www.winpcap.org/install/bin/WinPcap_4_1_1.exe>`_. You might want to choose "[x] Automatically start the WinPcap driver at boot time", so that non-privileged users can sniff, especially under Vista and Windows 7. If you want to use the ethernet vendor database to resolve MAC addresses or use the ``wireshark()`` command, download `Wireshark <http://www.wireshark.org/>`_ which already includes WinPcap. 
   * `pypcap <http://code.google.com/p/pypcap/>`_: `pcap-1.1-scapy-20090720.win32-py25.exe <http://www.secdev.org/projects/scapy/files/pcap-1.1-scapy-20090720.win32-py2.5.exe>`_. This is a *special version for Scapy*, as the original leads to some timing problems. Now works on Vista and Windows 7, too. Under Vista/Win7 please right-click on the installer and choose "Run as administrator".
   * `libdnet <http://code.google.com/p/libdnet/>`_:  `dnet-1.12.win32-py2.5.exe <http://libdnet.googlecode.com/files/dnet-1.12.win32-py2.5.exe>`_. Under Vista/Win7 please right-click on the installer and choose "Run as administrator"
   * `pyreadline <http://ipython.scipy.org/moin/PyReadline/Intro>`_: `pyreadline-1.5-win32-setup.exe <http://ipython.scipy.org/dist/pyreadline-1.5-win32-setup.exe>`_