Better detection of AltGr on Windows

Try to properly detect the fake CtrlL+AltR sequence Windows sends
when pressing AltGr. This allows us to send more accurate key
events over to the server.
diff --git a/doc/keyboard-test.txt b/doc/keyboard-test.txt
index 914b8eb..6375a9e 100644
--- a/doc/keyboard-test.txt
+++ b/doc/keyboard-test.txt
@@ -66,7 +66,7 @@
 
   - CapsLock, NumLock
   - Shift, Ctrl
-  - Alt, AltGr, Super [Win, X11] (FIXME: AltGr broken on Win)
+  - Alt, AltGr, Super [Win, X11] (FIXME: Ctrl+AltGr broken on Win)
   - Meta [X11]
   - Left/right identification (FIXME: broken for Shift on Win)
   - CmdL => AltL, CmdR => SuperL, AltL => ModeSwitch, AltR => Level3Shift [OS X]
@@ -74,8 +74,7 @@
 
   - CapsLock, Shift and AltGr affect symbol lookup
   - Ctrl does not affect symbol lookup
-  - CtrlL+AltR is fake released to compensate for Windows' AltGr magic [Win]
-  - Ctrl+Alt+<ANY> sends the same symbol as <ANY> (note behaviour above though)
+  - Ctrl+Alt+<ANY> sends the same symbol as <ANY>
   - Ctrl+AltGr+<ANY> sends the same symbol as AltGr+<ANY> (FIXME: broken on Win)
   - "Shift press, A press, Shift release, A release" should not send "a release"
 
@@ -128,8 +127,6 @@
   - Multimedia keys
   - Non-character keys
 
-- CtrlL+AltR is fake released to compensate for Windows' AltGr magic [Win]
-
 Client (both modes)
 -------------------