CLEANUP: threads: rename process_mask to thread_mask

It was a leftover from the last cleaning session; this mask applies
to threads and calling it process_mask is a bit confusing. It's the
same in fd, task and applets.
diff --git a/include/proto/applet.h b/include/proto/applet.h
index 766fc92..a6f2633 100644
--- a/include/proto/applet.h
+++ b/include/proto/applet.h
@@ -50,7 +50,7 @@
 {
 	appctx->st0 = appctx->st1 = appctx->st2 = 0;
 	appctx->io_release = NULL;
-	appctx->process_mask = thread_mask;
+	appctx->thread_mask = thread_mask;
 	appctx->state = APPLET_SLEEPING;
 }
 
diff --git a/include/proto/fd.h b/include/proto/fd.h
index 72af70f..e240f5c 100644
--- a/include/proto/fd.h
+++ b/include/proto/fd.h
@@ -404,7 +404,7 @@
 	fdtab[fd].linger_risk = 0;
 	fdtab[fd].cloned = 0;
 	fdtab[fd].cache = 0;
-	fdtab[fd].process_mask = thread_mask;
+	fdtab[fd].thread_mask = thread_mask;
 	SPIN_UNLOCK(FD_LOCK, &fdtab[fd].lock);
 
 	SPIN_LOCK(FDTAB_LOCK, &fdtab_lock);
diff --git a/include/proto/task.h b/include/proto/task.h
index cb98fef..6a89cd9 100644
--- a/include/proto/task.h
+++ b/include/proto/task.h
@@ -127,11 +127,12 @@
 	return t;
 }
 
+/* change the thread affinity of a task to <thread_mask> */
 static inline void task_set_affinity(struct task *t, unsigned long thread_mask)
 {
-
-	t->process_mask = thread_mask;
+	t->thread_mask = thread_mask;
 }
+
 /*
  * Unlink the task from the wait queue, and possibly update the last_timer
  * pointer. A pointer to the task itself is returned. The task *must* already
@@ -202,7 +203,7 @@
 	t->wq.node.leaf_p = NULL;
 	t->rq.node.leaf_p = NULL;
 	t->pending_state = t->state = TASK_SLEEPING;
-	t->process_mask = thread_mask;
+	t->thread_mask = thread_mask;
 	t->nice = 0;
 	t->calls = 0;
 	t->expire = TICK_ETERNITY;
diff --git a/include/types/applet.h b/include/types/applet.h
index b56c563..1c469a5 100644
--- a/include/types/applet.h
+++ b/include/types/applet.h
@@ -67,7 +67,7 @@
 	                                               if the command is terminated or the session released */
 	int cli_severity_output;        /* used within the cli_io_handler to format severity output of informational feedback */
 	struct buffer_wait buffer_wait; /* position in the list of objects waiting for a buffer */
-	unsigned long process_mask;     /* mask of thread IDs authorized to process the applet */
+	unsigned long thread_mask;      /* mask of thread IDs authorized to process the applet */
 
 	union {
 		struct {
diff --git a/include/types/fd.h b/include/types/fd.h
index e196aec..2da6599 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -94,7 +94,7 @@
 struct fdtab {
 	void (*iocb)(int fd);                /* I/O handler */
 	void *owner;                         /* the connection or listener associated with this fd, NULL if closed */
-	unsigned long process_mask;          /* mask of thread IDs authorized to process the task */
+	unsigned long thread_mask;           /* mask of thread IDs authorized to process the task */
 #ifdef USE_THREAD
 	HA_SPINLOCK_T lock;
 #endif
diff --git a/include/types/task.h b/include/types/task.h
index 799e6c5..236324d 100644
--- a/include/types/task.h
+++ b/include/types/task.h
@@ -72,7 +72,7 @@
 	void *context;			/* the task's context */
 	struct eb32_node wq;		/* ebtree node used to hold the task in the wait queue */
 	int expire;			/* next expiration date for this task, in ticks */
-	unsigned long process_mask;	/* mask of thread IDs authorized to process the task */
+	unsigned long thread_mask;	/* mask of thread IDs authorized to process the task */
 };
 
 /*