Upgrade Npcap to NDIS 6.20

[fyodor]

Our first step toward upgrading to the latest NDIS version is an upgrade to 6.20. This one supports all the operating systems that we currently do, and we think/home it may just need a preprocessor symbol definition to upgrade rather than any material code changes. This is a first step toward eventually supporting NDIS 6.50 for Windows 10. (I'm creating a separate issue for that part)

[fyodor]

New Update from @dmiller-nmap: Built 0.9992 with NDIS 6.20 for testing. Build is fine, but loopback capture is messed up. I've isolated the problem (unregistering WFP resources but failing to re-register when they are needed again) but will need a bit more time to make a solution. Idea I have in mind may make listing adapters faster: introduce a new state "open but not capturing" that delays some startup functions until buffer is intialized, since listing adapters results in opening every single one for a moment, but not setting a buffer size.

[guyharris]

Speaking of speeding up listing adapters, see also #169.

[guyharris]

Note that, with NDIS 6.20, you might have to use MediaSpecificInformationEx, rather than MediaSpecificInformation, to get the media-specific information on 802.11 adapters in monitor mode. See the NDIS_NET_BUFFER_LIST_INFO enumeration page and the NDIS_NBL_MEDIA_SPECIFIC_INFORMATION_EX structure page.

[dmiller-nmap]

Accomplished in 59a0625, but I will check on those OIDs, @guyharris. Thanks!

[dmiller-nmap]

Npcap 0.9993 included all changes needed to meet NDIS 6.20 compatibility.