move set_nonblock, create_socket and path_exists to libi3

libi3/path_exists.c

@@ -0,0 +1,21 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ */
+#include "libi3.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/*
+ * Checks if the given path exists by calling stat().
+ *
+ */
+bool path_exists(const char *path) {
+    struct stat buf;
+    return (stat(path, &buf) == 0);
+}