Fix missing text input on Windows with certain keyboard layouts

Events for keys specific to certain keyboard layouts unknown to Blender
were ignored. Now pass them along as unknown key events for which we
can still handle text input, like we already do for Linux and macOS.

Differential Revision: https://developer.blender.org/D7229

intern/ghost/intern/GHOST_SystemWin32.cpp

@@ -1044,7 +1044,10 @@ GHOST_EventKey *GHOST_SystemWin32::processKeyEvent(GHOST_WindowWin32 *window, RA
   GHOST_TKey key = system->hardKey(raw, &keyDown, &vk);
   GHOST_EventKey *event;
 
-  if (key != GHOST_kKeyUnknown) {
+  /* We used to check `if (key != GHOST_kKeyUnknown)`, but since the message
+   * values `WM_SYSKEYUP`, `WM_KEYUP` and `WM_CHAR` are ignored, we capture
+   * those events here as well. */
+  {
     char utf8_char[6] = {0};
     char ascii = 0;
     bool is_repeat = false;
@@ -1102,9 +1105,6 @@ GHOST_EventKey *GHOST_SystemWin32::processKeyEvent(GHOST_WindowWin32 *window, RA
 
     // GHOST_PRINTF("%c\n", ascii); // we already get this info via EventPrinter
   }
-  else {
-    event = NULL;
-  }
   return event;
 }