Implement autostart using "exec" in config

Syntax is "exec <application>", like when creating a binding.
Multiple entries are possible, applications are started in
the specified order.

src/mainx.c

@@ -52,6 +52,9 @@ Display *xkbdpy;
 /* The list of key bindings */
 struct bindings_head bindings = TAILQ_HEAD_INITIALIZER(bindings);
 
+/* The list of exec-lines */
+struct autostarts_head autostarts = TAILQ_HEAD_INITIALIZER(autostarts);
+
 /* This is a list of Stack_Windows, global, for easier/faster access on expose events */
 struct stack_wins_head stack_wins = SLIST_HEAD_INITIALIZER(stack_wins);
 
@@ -527,6 +530,13 @@ int main(int argc, char *argv[], char *env[]) {
                 }
         }
 
+        /* Autostarting exec-lines */
+        Autostart *exec;
+        TAILQ_FOREACH(exec, &autostarts, autostarts) {
+                LOG("auto-starting %s\n", exec->command);
+                start_application(exec->command);
+        }
+
         /* check for Xinerama */
         LOG("Checking for Xinerama...\n");
         initialize_xinerama(conn);