Set default binding for keyboard.

We set using the QWERT keyboard as a reference. These keys should
be located at fixed positions on most QWERT keyboards.

KEY    | KEYBOARD
-------|----------
UP     | W
DOWN   | S
LEFT   | A
RIGHT  | D
A      | L
B      | K
R      | O
L      | I
SELECT | Backspace
START  | Enter

- Fix #463.

src/wx/opts.cpp

@@ -143,9 +143,9 @@ const wxString joynames[NUM_KEYS] = {
 };
 
 wxJoyKeyBinding defkeys_keyboard[NUM_KEYS] = {
-    WJKB(WXK_UP), WJKB(WXK_DOWN), WJKB(WXK_LEFT), WJKB(WXK_RIGHT),
-    WJKB(wxT('A')), WJKB(wxT('S')), WJKB(wxT('Q')), WJKB(wxT('W')),
-    WJKB(wxT('Z')), WJKB(wxT('X')),
+    WJKB(wxT('W')), WJKB(wxT('S')), WJKB(wxT('A')), WJKB(wxT('D')),
+    WJKB(wxT('L')), WJKB(wxT('K')), WJKB(wxT('I')), WJKB(wxT('O')),
+    WJKB(WXK_BACK), WJKB(WXK_RETURN),
     WJKB(0), WJKB(0), WJKB(0), WJKB(0),
     WJKB(0), WJKB(0), WJKB(0), WJKB(0),
     WJKB(WXK_SPACE), WJKB(0), WJKB(0)