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.

Makefile

@@ -1,11 +1,11 @@
-all: pcat service service2
+all: pcat service1 service2
 
 pcat: pcat.cpp
-	clang++ pcat.cpp -o pcat
+	${CXX} pcat.cpp -o pcat
 
-service: service.cpp
-	clang++ service.cpp -o service
+1service1: service1.cpp
+	${CXX} service1.cpp -o service1
 
 service2: service2.cpp
-	clang++ service2.cpp -l pthread -o service2
+	${CXX} service2.cpp -l pthread -o service2