Fix for issue 643 - Support multiple HID controllers.

[gilesep]

Hi Nintendont team,

Thank you so much for developing Nintendont.

Please could you consider merging this PR? What it does is to fix issue 643 (related issue 213) and allow us to use splitters like this one (https://m.media-amazon.com/images/W/IMAGERENDERING_521856-T1/images/I/71HtURmbXOL._AC_SX522_.jpg) so we can have multiple gamepads working at the same time.

The splitters can be configured via the ini controller configuration files using a new mode "MultiIn=4". An example ini file called "controller_psx_ps2_splitter.ini" has been added, which works for the PSX/PS2 splitter I have at home.

I decided to introduce a new "MultiIn=4" mode, instead of just changing the code for the existing "MultiIn=2" mode, in case anyone was relying on the existing behavior and because I am using the MultiInValue differently (to represent the number of controllers supported instead of the index of the first controller).

If you need a binary to approve the PR, I have made one at https://github.com/gilesep/Nintendont-gi/releases/tag/v1.0.0.

I am not very familiar with GitHub or contributing to open source projects, so I hope this PR is ok.

Best wishes, Gi

[gilesep]

Sorry, closing this pull request as I think it is better to make it from the relevant branch rather than from master. I'll make another one. Best wishes, Gi