Messages: try to fix API message handling

Passed timeout for messeages an popup's fired by yWeb API was not really
ok.
For popups now we have a setting with default value of 6 seconds timeout
Popups fired with ShowHint() use this as default. Value of 0 and -1
are ignored.
Messages fired with ShowMsg() should be fixed and interpret
value 0 or -1 as no timeout and will remain on the screen.

src/system/locals_intern.h

@@ -2433,6 +2433,7 @@ const char * locale_real_names[] =
 	"timing.infobar_radio",
 	"timing.menu",
 	"timing.numericzap",
+	"timing.popup_messages",
 	"timing.volumebar",
 	"tmdb.api_key",
 	"tmdb.enabled",