Switch some Conf settings over to being bool.

I think this is the full set of things that ought logically to be
boolean.

One annoyance is that quite a few radio-button controls in config.c
address Conf fields that are now bool rather than int, which means
that the shared handler function can't just access them all with
conf_{get,set}_int. Rather than back out the rigorous separation of
int and bool in conf.c itself, I've just added a similar alternative
handler function for the bool-typed ones.

fuzzterm.c

@@ -25,7 +25,7 @@ int main(int argc, char **argv)
 	conf = conf_new();
 	do_defaults(NULL, conf);
 	init_ucs(&ucsdata, conf_get_str(conf, CONF_line_codepage),
-		 conf_get_int(conf, CONF_utf8_override),
+		 conf_get_bool(conf, CONF_utf8_override),
 		 CS_NONE, conf_get_int(conf, CONF_vtmode));
 
 	term = term_init(conf, &ucsdata, &termwin);
@@ -188,6 +188,11 @@ char *platform_default_s(const char *name)
     return NULL;
 }
 
+bool platform_default_b(const char *name, bool def)
+{
+    return def;
+}
+
 int platform_default_i(const char *name, int def)
 {
     return def;