Remove is_shift_pressed() -- it's not been used since r4906.

[originally from svn r8666]
[r4906 == 7ecf13564a]

windows/window.c

@@ -110,7 +110,6 @@ static LPARAM pend_netevent_lParam = 0;
 static void enact_pending_netevent(void);
 static void flash_window(int mode);
 static void sys_cursor_update(void);
-static int is_shift_pressed(void);
 static int get_fullscreen_rect(RECT * ss);
 
 static int caret_x = -1, caret_y = -1;
@@ -1909,17 +1908,6 @@ static int is_alt_pressed(void)
     return FALSE;
 }
 
-static int is_shift_pressed(void)
-{
-    BYTE keystate[256];
-    int r = GetKeyboardState(keystate);
-    if (!r)
-	return FALSE;
-    if (keystate[VK_SHIFT] & 0x80)
-	return TRUE;
-    return FALSE;
-}
-
 static int resizing;
 
 void notify_remote_exit(void *fe)