make a 'runtests' make target that runs some 'unit test'-like tests. Fix crash when uid's without a password entry are encountered, return the uid as a string instead.

nethogs.h

@@ -63,7 +63,9 @@
 
 #define PROGNAME_WIDTH 512
 
-void forceExit(const char *msg, int errcode, ...);
+#define NORETURN __attribute__ ((__noreturn__))
+
+void forceExit(bool success, const char *msg, ...) NORETURN;
 
 class local_addr {
 public:
@@ -128,4 +130,6 @@ private:
 
 void quit_cb (int i);
 
+const char* getVersion();
+
 #endif