quagga: option "-z" ("--socket <path>") added

All daemons modified to support custom path to zserv
socket.

lib: generalize a zclient connection

zclient_socket_connect added. zclient_socket and
zclient_socket_un were hidden under static expression.
"zclient_serv_path_set" modified.
diff --git a/ripd/rip_main.c b/ripd/rip_main.c
index 57b5f3a..ccb5fa0 100644
--- a/ripd/rip_main.c
+++ b/ripd/rip_main.c
@@ -32,6 +32,7 @@
 #include "log.h"
 #include "privs.h"
 #include "sigevent.h"
+#include "zclient.h"
 
 #include "ripd/ripd.h"
 
@@ -41,6 +42,7 @@
   { "daemon",      no_argument,       NULL, 'd'},
   { "config_file", required_argument, NULL, 'f'},
   { "pid_file",    required_argument, NULL, 'i'},
+  { "socket",      required_argument, NULL, 'z'},
   { "help",        no_argument,       NULL, 'h'},
   { "dryrun",      no_argument,       NULL, 'C'},
   { "vty_addr",    required_argument, NULL, 'A'},
@@ -109,6 +111,7 @@
 -d, --daemon       Runs in daemon mode\n\
 -f, --config_file  Set configuration file name\n\
 -i, --pid_file     Set process identifier file name\n\
+-z, --socket       Set path of zebra socket\n\
 -A, --vty_addr     Set vty's bind address\n\
 -P, --vty_port     Set vty's port number\n\
 -C, --dryrun       Check configuration for validity and exit\n\
@@ -206,7 +209,7 @@
     {
       int opt;
 
-      opt = getopt_long (argc, argv, "df:i:hA:P:u:g:rvC", longopts, 0);
+      opt = getopt_long (argc, argv, "df:i:z:hA:P:u:g:rvC", longopts, 0);
     
       if (opt == EOF)
 	break;
@@ -227,6 +230,9 @@
         case 'i':
           pid_file = optarg;
           break;
+	case 'z':
+	  zclient_serv_path_set (optarg);
+	  break;
 	case 'P':
           /* Deal with atoi() returning 0 on failure, and ripd not
              listening on rip port... */