signal: Add example of signal handler in Python.

signal/example_sigint.py

@@ -0,0 +1,17 @@
+import time
+from signal import *
+
+quit = 0
+
+def handler(signum):
+    global quit
+    quit = 1
+    print('Signal handler called with signal', signum)
+
+print("org signal() val:", signal(SIGINT, handler))
+print("read back signal() val:", signal(SIGINT, handler))
+
+while not quit:
+    time.sleep(10)
+
+print("Quitting...")