MINOR: config: keep an all_proc_mask like we have all_threads_mask

This simplifies some mask comparisons at various places where
nbits(global.nbproc) was used.
diff --git a/src/haproxy.c b/src/haproxy.c
index 5a69086..ce4cde3 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -129,6 +129,7 @@
 int  pid;			/* current process id */
 int  relative_pid = 1;		/* process id starting at 1 */
 unsigned long pid_bit = 1;      /* bit corresponding to the process id */
+unsigned long all_proc_mask = 1; /* mask of all processes */
 
 volatile unsigned long sleeping_thread_mask; /* Threads that are about to sleep in poll() */
 /* global options */
@@ -903,6 +904,7 @@
 	global.nbthread = 1;
 	relative_pid = 1;
 	pid_bit = 1;
+	all_proc_mask = 1;
 
 #ifdef USE_THREAD
 	tid_bit = 1;