Input: remove unused stuff & clean up

1. removed zl, zr and c-stick from HID::PadState. They are handled by IR, not HID
2. removed button handling in EmuWindow
3. removed key_map
4. cleanup #include

src/core/CMakeLists.txt

@@ -34,7 +34,6 @@ set(SRCS
             frontend/camera/factory.cpp
             frontend/camera/interface.cpp
             frontend/emu_window.cpp
-            frontend/key_map.cpp
             frontend/motion_emu.cpp
             gdbstub/gdbstub.cpp
             hle/config_mem.cpp
@@ -219,7 +218,6 @@ set(HEADERS
             frontend/camera/interface.h
             frontend/emu_window.h
             frontend/input.h
-            frontend/key_map.h
             frontend/motion_emu.h
             gdbstub/gdbstub.h
             hle/config_mem.h