Allow Win32 installer to set WinPcap destination dir in silent mode

[dmiller-nmap]

Report: https://serverfault.com/questions/759086/nmap-silent-with-specific-installation-directory

Previous report: http://seclists.org/nmap-dev/2008/q2/834

In silent mode, we allow setting the destination directory for Nmap with /D, but WinPcap always installs to its default directory. The bundled WinPcap installer accepts /D also, so we just need a new parameter to pass along from the Nmap installer.

[fyodor]

I'm closing this since we haven't shipped WinPcap in years. Also only Nmap OEM and Npcap OEM have silent installers. If there is demand we could look at a general way to pass certain Npcap options through the Nmap installer. But probably the easiest approach in the rare case that customer Npcap options are needed is to run Npcap OEM silent installer with whatever options you want (including /D to set destination directory) and then run Nmap silent installer (which will see Npcap is already installed and skip that). For non-silent Nmap and Npcap installers, there is a GUI for selecting installation directory for each.