continued with draw.c abstraction, also started util.{h,c} implementation, that will be used by draw.c as well

util.c

@@ -0,0 +1,17 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "util.h"
+
+void
+die(const char *errstr, ...) {
+	va_list ap;
+
+	va_start(ap, errstr);
+	vfprintf(stderr, errstr, ap);
+	va_end(ap);
+	exit(EXIT_FAILURE);
+}
+