Tile root pixmap in the glx backend

In X, background pixmap is tiled (meaning they are repeated to filled
the window) by default. So, in the glx backend, we mimic this behavior
by binding the background pixmap of the root window (aka, the wallpaper)
to texture that repeats.

Fixes #107

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/log.c

@@ -103,8 +103,8 @@ void log_add_target(struct log *l, struct log_target *tgt) {
 	l->head = tgt;
 }
 
-/// Remove a previously added log target for a log struct. If the log target was never
-/// added, nothing happens.
+/// Remove a previously added log target for a log struct, and destroy it. If the log
+/// target was never added, nothing happens.
 void log_remove_target(struct log *l, struct log_target *tgt) {
 	struct log_target *now = l->head, **prev = &l->head;
 	while (now) {