* Add MinGW and WinXP support, remove Win SDK dep when using MinGW
* Remove Win SDK dependency when compiled with MinGW
* Remap the Win SDK-depended functions to string.h substitutes
* Remap missing WinAPI call RegSetKeyValueW to a substitute function
* Remove warnings by pragma when using MinGW
* Fix segfaults in Discord_RegisterW in MinGW builds
* Add MinGW and WinXP support, remove Win SDK dep when using MinGW
Was meant to add MinGW support only, WinXP support was made by accident.
Changes:
* Remove Win SDK dependency when compiled with MinGW
* Remap the Win SDK-depended functions to string.h substitutes
* Remap missing WinAPI call RegSetKeyValueW to a substitute function
* Remove warnings by pragma when using MinGW
As per
https://msdn.microsoft.com/en-us/library/windows/desktop/ms683198(v=vs.85).aspx,
the advised use for getting the file name of a module from `<current
process>` is to use the simplified version. Additionally, this clears
the confusion introduced in Win7's PSAPI which moved
`GetModuleFileNameExW` into the kernel, changing its signature to
`K32GetModuleFileNameExW`, effectively breaking pre-Win7 uses unless
actively mitigated with `#define PSAPI_VERSION 1`
