Remove dead code guarded with "#if 0 … #endif" (#2338)

This code has been neutralized for many years now and served no purpose
other than cluttering up the code. We obviously don't need it and it's
out of date anyway.

If there's ever any reason to restore (parts of) it, we have git for
that. But we don't need to keep commented out code around.

include/manage.h

@@ -35,19 +35,3 @@ void restore_geometry(void);
 void manage_window(xcb_window_t window,
                    xcb_get_window_attributes_cookie_t cookie,
                    bool needs_to_be_mapped);
-
-#if 0
-/**
- * reparent_window() gets called when a new window was opened and becomes a
- * child of the root window, or it gets called by us when we manage the
- * already existing windows at startup.
- *
- * Essentially, this is the point where we take over control.
- *
- */
-void reparent_window(xcb_connection_t *conn, xcb_window_t child,
-                     xcb_visualid_t visual, xcb_window_t root, uint8_t depth,
-                     int16_t x, int16_t y, uint16_t width, uint16_t height,
-                     uint32_t border_width);
-
-#endif