MINOR: contrib: make the peers wireshark dissector a plugin

The wireshark dissector could only be build within wireshark, which
means maintaining a wireshark binary just for this dissector. It was not
really convenient to update wireshark because of this.

This patch converts the dissector into a .so plugin which is built with
the .h found in distributions instead of the whole wireshark sources.
diff --git a/contrib/wireshark-dissectors/peers/Makefile b/contrib/wireshark-dissectors/peers/Makefile
new file mode 100644
index 0000000..9e70802
--- /dev/null
+++ b/contrib/wireshark-dissectors/peers/Makefile
@@ -0,0 +1,17 @@
+CFLAGS = `pkg-config --cflags wireshark` -g -fPIC
+LDFLAGS = `pkg-config --libs wireshark`
+
+NAME = packet-happp.so
+OBJS = packet-happp.o
+
+plugins=$(HOME)/.wireshark/plugins/
+
+$(NAME): $(OBJS)
+	$(CC) -shared $(LDFLAGS) $(OBJS) -o $@
+
+install: $(NAME)
+	install -d $(DESTDIR)$(plugins)
+	install -m 0755 $(NAME) $(DESTDIR)$(plugins)
+
+clean:
+	rm $(NAME) $(OBJS)