XEP-0092: Add configuration option to choose whether to send OS name

`/os on|off` now let's one choose whether to include the OS name once
`/software` (XEP-0092) is ran on us.

src/command/cmd_ac.c

@@ -1508,7 +1508,7 @@ _cmd_ac_complete_params(ProfWin *window, const char *const input, gboolean previ
 
     // autocomplete boolean settings
     gchar *boolean_choices[] = { "/beep", "/intype", "/states", "/outtype", "/flash", "/splash",
-        "/history", "/vercheck", "/privileges", "/wrap", "/carbons", "/lastactivity"};
+        "/history", "/vercheck", "/privileges", "/wrap", "/carbons", "/lastactivity", "/os"};
 
     for (i = 0; i < ARRAY_SIZE(boolean_choices); i++) {
         result = autocomplete_param_with_func(input, boolean_choices[i], prefs_autocomplete_boolean_choice, previous);

src/command/cmd_defs.c

@@ -2344,6 +2344,21 @@ static struct cmd_t command_defs[] =
             { "<barejid>", "JID to download avatar from."})
         CMD_NOEXAMPLES
     },
+
+    { "/os",
+        parse_args, 1, 1, &cons_os_setting,
+        CMD_NOSUBFUNCS
+        CMD_MAINFUNC(cmd_os)
+        CMD_TAGS(
+            CMD_TAG_DISCOVERY)
+        CMD_SYN(
+            "/os <on>|<off>")
+        CMD_DESC(
+            "Choose whether to include the OS name if a user asks for software information (XEP-0092).")
+        CMD_ARGS(
+            { "on|off", ""})
+        CMD_NOEXAMPLES
+    },
 };
 
 static GHashTable *search_index;

src/command/cmd_funcs.c

@@ -8640,3 +8640,11 @@ cmd_avatar(ProfWin *window, const char *const command, gchar **args)
 
     return TRUE;
 }
+
+gboolean
+cmd_os(ProfWin *window, const char *const command, gchar **args)
+{
+    _cmd_set_boolean_preference(args[0], command, "Revealing OS name", PREF_REVEAL_OS);
+
+    return TRUE;
+}

src/command/cmd_funcs.h

@@ -226,4 +226,5 @@ gboolean cmd_reload(ProfWin *window, const char *const command, gchar **args);
 gboolean cmd_paste(ProfWin *window, const char *const command, gchar **args);
 gboolean cmd_color(ProfWin *window, const char *const command, gchar **args);
 gboolean cmd_avatar(ProfWin *window, const char *const command, gchar **args);
+gboolean cmd_os(ProfWin *window, const char *const command, gchar **args);
 #endif