support multiple usage/usage-pages on macOS, update of @fengj2006 PR#65

[todbot]

I think this includes all the requested changes, on top of the work done by @fengj2006 on #65

You can now see all the different usages as different "devices" in hid_enumerate(). When running hidtest you see them too. On a Macbook with internal keyboard/trackpad, there are many:

% ./hidtest | grep -E "(Product|Usage)"
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x3 (0xff00)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0xd (0xff00)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x2 (0x1)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x1 (0x1)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x5 (0xd)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0xc (0xff00)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x6 (0x1)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x1 (0xc)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0x6 (0xff00)
  Product:      Apple Internal Keyboard / Trackpad
  Usage (page): 0xb (0xff00)

Additionally, I've verified that an Arduino "RawHID" device with two usages shows up as two devices to hidapi

(the device is a $9 Trinket M0 running TinyUSB pretending to like Teensy in RawHID mode) You can see this here: https://github.com/todbot/hidapitester/tree/master/tinyusb_teensyrawhid_multiusage

[Youw]

@todbot:
I mean this function and all of the below shouldn't be changed at all
see 083223e and d64f6c6

[todbot]

oh! okay I will not try to use any merge tools and instead re-do this PR by hand. I didn't think fengj2006's original PR was so far back in time. sigh.

[Youw]

yeah, I guess it was

a hint:

• checkout fengj2006's branch
• save a diff only: git diff HEAD~1 > diff.diff
  so it only contain a relevant changes
• checkout to origin/master
• apply diff: git apply diff.diff

[Youw]

oh, you've already done it :)