Add ic706* rigs to mode_731. They are part of the gang that have 8-digit freqencies and can read passband but can't select passband.

According to the CI-V+ manual the IC-781, IC-R9000, and IC-R7000 can select passband.
The other rigs listed apparently cannot...notes added to icom.h on this
1-706
2-706MKII
3-706MKIIG
4-707
5-718
6-746
7-746PRO
8-756
9-756PRO
10-756PROII
11-820H
12-821H
13-910H
14-R10
15-R8500
16-703
17-7800

rigs/icom/ic706.c

@@ -141,7 +141,7 @@ static int ic706_r2i_mode(RIG *rig, rmode_t mode, pbwidth_t width,
 static const struct icom_priv_caps ic706_priv_caps =
 {
     0x48,   /* default address */
-    0,      /* 731 mode */
+    1,      /* 731 mode */
     0,    /* no XCHG */
     ic706_ts_sc_list,
     .serial_USB_echo_check = 1,  /* USB CI-V may not echo */
@@ -279,7 +279,7 @@ const struct rig_caps ic706_caps =
 static const struct icom_priv_caps ic706mkii_priv_caps =
 {
     0x4e,   /* default address */
-    0,      /* 731 mode */
+    1,      /* 731 mode */
     0,    /* no XCHG */
     ic706_ts_sc_list,
     .serial_USB_echo_check = 1,  /* USB CI-V may not echo */
@@ -441,7 +441,7 @@ const struct rig_caps ic706mkii_caps =
 static const struct icom_priv_caps ic706mkiig_priv_caps =
 {
     0x58,   /* default address */
-    0,      /* 731 mode */
+    1,      /* 731 mode */
     0,    /* no XCHG */
     ic706_ts_sc_list,
     .serial_USB_echo_check = 1,  /* USB CI-V may not echo */
@@ -453,7 +453,7 @@ const struct rig_caps ic706mkiig_caps =
     .rig_model =  RIG_MODEL_IC706MKIIG,
     .model_name = "IC-706MkIIG",
     .mfg_name =  "Icom",
-    .version =  BACKEND_VER ".3",
+    .version =  BACKEND_VER ".4",
     .copyright =  "LGPL",
     .status =  RIG_STATUS_STABLE,
     .rig_type =  RIG_TYPE_MOBILE,