tools: add a debug-device utility

[whot]

This one simply prints all return values for a device from our API, making it easier to figure out the exact behavior of a device. This is a debug utility so it is not installed.

Example output:
libwacom_get_name() -> "Wacom Cintiq 24HD touch"
libwacom_get_model_name() -> "DTH-2400"
libwacom_get_layout_filename() -> "data/layouts/cintiq-24hd.svg"
libwacom_get_vendor_id() -> 0x56a
libwacom_get_product_id() -> 0xf8
libwacom_get_bustype() -> USB
libwacom_get_width() -> 21
libwacom_get_height() -> 13
libwacom_is_reversible() -> 0

---

cc @JoseExposito

[JoseExposito]

Added a few minor comments, looking really good. For reference, this is the output for my Hioun tablet:

libwacom_get_name()                      -> "Huion H640P"
libwacom_get_model_name()                -> "(null)"
libwacom_get_layout_filename()           -> "/home/jexposit/Devel/libwacom/data/layouts/huion-h640p.svg"
libwacom_get_vendor_id()                 -> 0x256c
libwacom_get_product_id()                -> 0x006d
libwacom_get_bustype()                   -> USB
libwacom_get_width()                     -> 6
libwacom_get_height()                    -> 4
libwacom_is_reversible()                 -> 1
libwacom_get_matches() -> {
  {
    libwacom_match_get_match_string()        -> "usb|256c|006d|HUION Huion Tablet_H640P Pad"
    libwacom_match_get_name()                -> "HUION Huion Tablet_H640P Pad"
    libwacom_match_get_uniq()                -> "(null)"
    libwacom_match_get_bustype()             -> 0x0001
    libwacom_match_get_vendor_id()           -> 0x256c
    libwacom_match_get_product_id()          -> 0x006d
  }
  {
    libwacom_match_get_match_string()        -> "usb|256c|006d|HUION Huion Tablet_H640P Pen"
    libwacom_match_get_name()                -> "HUION Huion Tablet_H640P Pen"
    libwacom_match_get_uniq()                -> "(null)"
    libwacom_match_get_bustype()             -> 0x0001
    libwacom_match_get_vendor_id()           -> 0x256c
    libwacom_match_get_product_id()          -> 0x006d
  }
}
libwacom_get_match()                     -> "usb|256c|006d|HUION Huion Tablet_H640P Pad"
libwacom_get_paired_device() -> {<none>
}
libwacom_has_stylus()                    -> 1
libwacom_has_touch()                     -> 0
libwacom_get_num_buttons()               -> 6
libwacom_get_num_keys()                  -> 0
libwacom_has_ring()                      -> 0
libwacom_has_ring2()                     -> 0
libwacom_has_touchswitch()               -> 0
libwacom_get_ring_num_modes()            -> 0
libwacom_get_ring2_num_modes()           -> 0
libwacom_get_num_strips()                -> 0
libwacom_get_strips_num_modes()          -> 0
libwacom_get_integration_flags()         -> NONE 
libwacom_get_button_led_group('A')       -> -1
libwacom_get_button_led_group('B')       -> -1
libwacom_get_button_led_group('C')       -> -1
libwacom_get_button_led_group('D')       -> -1
libwacom_get_button_led_group('E')       -> -1
libwacom_get_button_led_group('F')       -> -1
libwacom_get_button_evdev_code('A')      -> 0x100
libwacom_get_button_evdev_code('B')      -> 0x101
libwacom_get_button_evdev_code('C')      -> 0x102
libwacom_get_button_evdev_code('D')      -> 0x103
libwacom_get_button_evdev_code('E')      -> 0x104
libwacom_get_button_evdev_code('F')      -> 0x105
libwacom_get_button_flag('A')            -> POSITION_LEFT|
libwacom_get_button_flag('B')            -> POSITION_LEFT|
libwacom_get_button_flag('C')            -> POSITION_LEFT|
libwacom_get_button_flag('D')            -> POSITION_LEFT|
libwacom_get_button_flag('E')            -> POSITION_LEFT|
libwacom_get_button_flag('F')            -> POSITION_LEFT|
libwacom_get_status_leds()               -> []
libwacom_get_supported_styli()           -> [0x0ffffd]

[whot]

Thanks, all review comments addressed and I added the --with-styli ability to print the same info about the compatible styli - which will also come in handy for debugging one day.

Plus a small change in the printing to align the output better.

[JoseExposito]

Thanks for the quick fixes, LGTM