Add payload, probe, and matchline for svrloc

Service Location Protocol version 2 specified by RFC 2608. Partially
implemented by srvloc.lua library. Probe checks for
service:service-agent, which should be implemented by all Service Agents
(servers). Match line only matches version 2, since I don't have any
other versions to test. Expect we will get more service fingerprints to
clarify.

nmap-payloads

@@ -67,6 +67,11 @@ udp 161
 # http://cgit.freedesktop.org/xorg/doc/xorg-docs/plain/hardcopy/XDMCP/xdmcp.PS.gz
 udp 177 "\x00\x01\x00\x02\x00\x01\x00"
 
+# svrloc
+udp 427
+  "\x02\x01\x00\x006 \x00\x00\x00\x00\x00\x01\x00\x02en\x00\x00\x00\x15"
+  "service:service-agent\x00\x07default\x00\x00\x00\x00"
+
 # Internet Key Exchange version 1, phase 1 Main Mode. We offer every
 # combination of (DES, 3DES) and (MD5, SHA) in the hope that one of them will
 # be acceptable. Because we use a fixed cookie, we set the association lifetime

nmap-service-probes

@@ -11832,3 +11832,10 @@ rarity 9
 ports 50505,55552
 sslports 3790
 match metasploit-msgrpc m|^HTTP/1\.1 200 OK\r\nContent-Type: binary/message-pack\r\nConnection: close\r\nServer: Rex\r\nContent-Length: 1084\r\n\r\n\x85\xa5error\xc3\xaberror_class\xadArgumentError\xacerror_string\xbdInvalid Request Verb: '\"GET\"'\xaferror_backtrace\xdc\x00\x12\xda\x000lib/msf/core/rpc/v10/service\.rb:107:in `process'\xda\x006lib/msf/core/rpc/v10/service\.rb:88:in `on_request_uri'\xda\x006lib/msf/core/rpc/v10/service\.rb:70:in `block in start'\xda\x00/lib/rex/proto/http/handler/proc\.rb:37:in `call'\xda\x005lib/rex/proto/http/handler/proc\.rb:37:in `on_request'\xda\x00| p/Metasploit Remote API/ v/4.4.0-dev/
+
+##############################NEXT PROBE##############################
+# svrloc
+Probe UDP svrloc q|\x02\x01\x00\x006 \x00\x00\x00\x00\x00\x01\x00\x02en\x00\x00\x00\x15service:service-agent\x00\x07default\x00\x00\x00\x00|
+rarity 8
+ports 427
+match svrloc m|^\x02\x0b| p/Service Location Protocol/ v/2/