overlay: fixes for naive binding (#542)

## Description of change
Three bugs:

* Some keys are IME-dependent. Right Alt can be IME mode switch for
Japanese / Korean, and Right Ctrl is often the Kanji button.
* If you press modifiers like Ctrl during bind-many-naive, it will skip
over a button, because of broken for loop logic that ends up calling
`inc_buttons_many_index` too many times
* trying to cancel out of bind-many-naive with left and right mouse
buttons swap doesn't work

## Testing
Validating various IME. I don't have a keyboard in another language
though..

src/spice2x/cfg/button.cpp

@@ -58,8 +58,28 @@ std::string Button::getVKeyString() {
             return "Pause";
         case 0x14:
             return "Caps Lock";
+        case 0x15:
+            return "IME Kana/Hangul";
+        case 0x16:
+            return "IME On";
+        case 0x17:
+            return "IME Junja";
+        case 0x18:
+            return "IME Final";
+        case 0x19:
+            return "IME Hanja/Kanji";
+        case 0x1A:
+            return "IME Off";
         case 0x1B:
             return "Escape";
+        case 0x1C:
+            return "IME Convert";
+        case 0x1D:
+            return "IME Nonconvert";
+        case 0x1E:
+            return "IME Accept";
+        case 0x1F:
+            return "IME Mode Change";
         case 0x20:
             return "Space";
         case 0x21:
@@ -255,9 +275,9 @@ std::string Button::getVKeyString() {
         case 0xA3:
             return "Right Control";
         case 0xA4:
-            return "Left Menu";
+            return "Left Alt";
         case 0xA5:
-            return "Right Menu";
+            return "Right Alt";
         default:
 
             // check win API