Cleaner examples

- Use ${CXX} instead of explicit clang in the Makefile.
- More explanations.
- Use socat's fork option instead of a bash loop.
- Adds a run_* script for each example.
- Remove the useless "sleep" option in service2.

run_socat_server.sh

@@ -0,0 +1,7 @@
+
+./service1 data out &
+PID_SERVICE=$!
+
+socat -v -u TCP-LISTEN:8423,reuseaddr,fork PIPE:./data
+
+kill $PID_SERVICE