make it compile with modern Erlang (22.0)

... also do away with our local outdated copy of exprecs and use
upstream
diff --git a/src/osmo_ss7_pcap.erl b/src/osmo_ss7_pcap.erl
index 309b80a..ffa9d59 100644
--- a/src/osmo_ss7_pcap.erl
+++ b/src/osmo_ss7_pcap.erl
@@ -39,7 +39,7 @@
 -define(NODEBUG, 1).
 
 -include_lib("eunit/include/eunit.hrl").
--include_lib("epcap/include/epcap_net.hrl").
+-include_lib("pkt/include/pkt.hrl").
 
 -record(loop_data, {
 		args,