HTTP server example and DHCP Server rewrite (#38)

* improvements to dhcpv4 server

* begin adding examples/httpserver

* add better VLAN tagging methods

* pcap: add error printing; fix bug in CRC

* ipv4: ToS and Flags construction and flag manipulation improvements

* add dhcp interception to httptap and improve httpserver example

.gitignore

@@ -25,6 +25,8 @@ vendor/
 /xcurl
 /xnet
 /httpclient
+/httpserver
+**/local*
 /stack
 **__debug_bin*
 # `__debug_bin` Debug binary generated in VSCode when using the built-in debugger.
@@ -33,6 +35,7 @@ vendor/
 /bridge
 # IDE
 .vscode/
+agents.md
 
 # For local development and testing create `local` directories.
 local