tests: Add example of how to use printhdr()

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

tests/printhdr.c

@@ -0,0 +1,20 @@
+#include <stdlib.h>		/* atexit() */
+#include <unistd.h>		/* usleep() */
+
+#include "check.h"
+
+#define SCREEN_WIDTH    80
+
+int main(void)
+{
+	FILE *fp = stderr;
+	char buf[SCREEN_WIDTH];
+
+	printhdr(fp, "", 0, UNDERSCORE);
+	printhdr(fp, "Neighbor Table", 0, 0);
+	snprintf(buf, sizeof(buf), "%-15s %-15s %7s %-5s%10s %6s",
+		 "Neighbor", "Interface", "Version", "Flags", "Uptime", "Expire");
+	printhdr(fp, buf, 0, REVERSE);
+
+	return 0;
+}