MINOR: config: Add threads support for "process" option on "bind" lines

It is now possible on a "bind" line (or a "stats socket" line) to specify the
thread set allowed to process listener's connections. For instance:

    # HTTPS connections will be processed by all threads but the first and HTTP
    # connection will be processed on the first thread.
    bind *:80 process 1/1
    bind *:443 ssl crt mycert.pem process 1/2-
diff --git a/include/types/listener.h b/include/types/listener.h
index b92c35e..c55569c 100644
--- a/include/types/listener.h
+++ b/include/types/listener.h
@@ -33,6 +33,7 @@
 #include <common/config.h>
 #include <common/mini-clist.h>
 #include <common/hathreads.h>
+#include <common/standard.h>
 
 #include <types/obj_type.h>
 #include <eb32tree.h>
@@ -159,6 +160,7 @@
 	int is_ssl;                /* SSL is required for these listeners */
 	int generate_certs;        /* 1 if generate-certificates option is set, else 0 */
 	unsigned long bind_proc;   /* bitmask of processes allowed to use these listeners */
+	unsigned long bind_thread[LONGBITS]; /* bitmask of threads (per processes) allowed to use these listeners */
 	struct {                   /* UNIX socket permissions */
 		uid_t uid;         /* -1 to leave unchanged */
 		gid_t gid;         /* -1 to leave unchanged */