Add an error for record coercions that would orphan a field.

These cases should be avoidable by fixing scripts where they occur and
they can also help catch typos that would lead to unintentional runtime
behavior.

Adding this already revealed several scripts where a field in an inlined
record was never removed after a code refactor.

scripts/base/protocols/http/file-hash.bro

@@ -73,7 +73,7 @@ event http_message_done(c: connection, is_orig: bool, stat: http_message_stat) &
 		delete c$http$md5_handle;
 		
 		NOTICE([$note=MD5, $msg=fmt("%s %s %s", c$id$orig_h, c$http$md5, url),
-		        $sub=c$http$md5, $conn=c, $URL=url]);
+		        $sub=c$http$md5, $conn=c]);
 		}
 	}
 

scripts/base/protocols/http/file-ident.bro

@@ -68,9 +68,7 @@ event signature_match(state: signature_state, msg: string, data: string) &priori
 		local message = fmt("%s %s %s", msg, c$http$method, url);
 		NOTICE([$note=Incorrect_File_Type,
 		        $msg=message,
-		        $conn=c,
-		        $method=c$http$method,
-		        $URL=url]);
+		        $conn=c]);
 		}
 	}