add i3-nagbar. tells you about config file errors (for example)

i3-nagbar/i3-nagbar.h

@@ -0,0 +1,26 @@
+#ifndef _I3_NAGBAR
+#define _I3_NAGBAR
+
+#include <err.h>
+
+#define die(...) errx(EXIT_FAILURE, __VA_ARGS__);
+#define FREE(pointer) do { \
+        if (pointer != NULL) { \
+                free(pointer); \
+                pointer = NULL; \
+        } \
+} \
+while (0)
+
+#define xmacro(atom) xcb_atom_t A_ ## atom;
+#include "atoms.xmacro"
+#undef xmacro
+
+extern xcb_window_t root;
+
+uint32_t get_colorpixel(xcb_connection_t *conn, char *hex);
+xcb_window_t open_input_window(xcb_connection_t *conn, uint32_t width, uint32_t height);
+int get_font_id(xcb_connection_t *conn, char *pattern, int *font_height);
+void xcb_change_gc_single(xcb_connection_t *conn, xcb_gcontext_t gc, uint32_t mask, uint32_t value);
+
+#endif