Qt key handling

Fix the popup versions of qt_yn_function() to handle control
characters by using the same key press event decoding routine
and menus and extended commands.  Moves 'keyValue()' to
qt_key.cpp and its declaration to qt_key.h, requring several
files to start using #include "qt_key.h".

'make depend' update to follow.

win/Qt/qt_menu.h

@@ -15,8 +15,6 @@
 
 namespace nethack_qt_ {
 
-extern uchar keyValue(QKeyEvent *key_event); // also used in qt_xcmd.cpp
-
 class NetHackQtTextListBox : public QListWidget {
 public:
     NetHackQtTextListBox(QWidget* parent = NULL) : QListWidget(parent) { }