Add buffer for IME editing events

When inputting uncommitted text from an IME, this is now stored in a
std::string imebuffer, just like keybuffer. It also enables extended
editing events, so text longer than what fits in the standard editing
event is also supported. This commit does not yet display the text
onscreen.

desktop_version/src/KeyPoll.cpp

@@ -50,7 +50,8 @@ KeyPoll::KeyPoll(void)
     // 0..5
     sensitivity = 2;
 
-    keybuffer="";
+    keybuffer = "";
+    imebuffer = "";
     leftbutton=0; rightbutton=0; middlebutton=0;
     mousex = 0;
     mousey = 0;
@@ -64,13 +65,15 @@ KeyPoll::KeyPoll(void)
 
 void KeyPoll::enabletextentry(void)
 {
-    keybuffer="";
+    keybuffer = "";
+    imebuffer = "";
     SDL_StartTextInput();
 }
 
 void KeyPoll::disabletextentry(void)
 {
     SDL_StopTextInput();
+    imebuffer = "";
 }
 
 bool KeyPoll::textentry(void)
@@ -321,6 +324,13 @@ void KeyPoll::Poll(void)
                 keybuffer += evt.text.text;
             }
             break;
+        case SDL_TEXTEDITING:
+            imebuffer = evt.edit.text;
+            break;
+        case SDL_TEXTEDITING_EXT:
+            imebuffer = evt.editExt.text;
+            SDL_free(evt.editExt.text);
+            break;
 
         /* Mouse Input */
         case SDL_MOUSEMOTION: