jobctl/tty: foreground/background and send sighup on unregister

kernel-src/include/kernel/jobctl.h

@@ -14,5 +14,7 @@ pid_t jobctl_getsid(proc_t *proc);
 void jobctl_setctty(proc_t *proc, void *ctty);
 void *jobctl_getctty(proc_t *proc);
 int jobctl_signal(proc_t *proc, int signal);
+proc_t *jobctl_getforeground(proc_t *proc);
+int jobctl_setforeground(proc_t *session, proc_t *pgrp);
 
 #endif

kernel-src/include/kernel/tty.h

@@ -28,6 +28,8 @@ typedef struct {
 	int minor;
 	winsize_t winsize;
 	vnode_t *mastervnode;
+	spinlock_t sessionlock;
+	struct proc_t *session;
 } tty_t;
 
 void tty_init();