adds implementation for SteamAPI_InitFlat

[Thelvaen]

Adds functions:

• steam_api_init_flat() : wrapper for the SDK call,
• init_flat() : copy of init(), but calls steam_api_init_flat() instead of steam_api_init_ex(),
• init_flat_app() : copy of init_app(), but calls init_flat() instead of init(),

[LZQCN]

Now, you can safely remove Client::steam_api_init_ex as it was merely a temporary workaround for 1.58a SDK, reason is valve forgot to expose the steam_api_init_flat function.

[Thelvaen]

Now, you can safely remove Client::steam_api_init_ex as it was merely a temporary workaround for 1.58a SDK, reason is valve forgot to expose the steam_api_init_flat function.

That would mean discard the existing init & init_app function and replace them with the implementation I provided?

I don't mind editing my PR in that direction, I'm just not sure as to what are the consequences of not initializing the SteamAPI with the ISteam Interface on our side, as it's what the previous version is doing (to my understanding).

[LZQCN]

The Client:: steam.api_init_ex function was added by me, due to it is hard-coded, it is highly likely to lack upward compatibility.

It is just to simulate this function:

steamworks-rs/steamworks-sys/lib/steam/public/steam/steam_api.h

Lines 338 to 372 in e596375

	S_API ESteamAPIInitResult S_CALLTYPE SteamInternal_SteamAPI_Init( const char *pszInternalCheckInterfaceVersions, SteamErrMsg *pOutErrMsg );
	inline ESteamAPIInitResult SteamAPI_InitEx( SteamErrMsg *pOutErrMsg )
	{
	const char *pszInternalCheckInterfaceVersions =
	STEAMUTILS_INTERFACE_VERSION "\0"
	STEAMNETWORKINGUTILS_INTERFACE_VERSION "\0"
	STEAMAPPS_INTERFACE_VERSION "\0"
	STEAMCONTROLLER_INTERFACE_VERSION "\0"
	STEAMFRIENDS_INTERFACE_VERSION "\0"
	STEAMGAMESEARCH_INTERFACE_VERSION "\0"
	STEAMHTMLSURFACE_INTERFACE_VERSION "\0"
	STEAMHTTP_INTERFACE_VERSION "\0"
	STEAMINPUT_INTERFACE_VERSION "\0"
	STEAMINVENTORY_INTERFACE_VERSION "\0"
	STEAMMATCHMAKINGSERVERS_INTERFACE_VERSION "\0"
	STEAMMATCHMAKING_INTERFACE_VERSION "\0"
	STEAMMUSICREMOTE_INTERFACE_VERSION "\0"
	STEAMMUSIC_INTERFACE_VERSION "\0"
	STEAMNETWORKINGMESSAGES_INTERFACE_VERSION "\0"
	STEAMNETWORKINGSOCKETS_INTERFACE_VERSION "\0"
	STEAMNETWORKING_INTERFACE_VERSION "\0"
	STEAMPARENTALSETTINGS_INTERFACE_VERSION "\0"
	STEAMPARTIES_INTERFACE_VERSION "\0"
	STEAMREMOTEPLAY_INTERFACE_VERSION "\0"
	STEAMREMOTESTORAGE_INTERFACE_VERSION "\0"
	STEAMSCREENSHOTS_INTERFACE_VERSION "\0"
	STEAMUGC_INTERFACE_VERSION "\0"
	STEAMUSERSTATS_INTERFACE_VERSION "\0"
	STEAMUSER_INTERFACE_VERSION "\0"
	STEAMVIDEO_INTERFACE_VERSION "\0"
	"\0";
	return SteamInternal_SteamAPI_Init( pszInternalCheckInterfaceVersions, pOutErrMsg );
	}

---

For the new version, the SteamAPI_InitFlat should be used:

steamworks-rs/steamworks-sys/lib/steam/public/steam/steam_api.h

Lines 77 to 79 in e596375

	// If you are unable to include this C++ header in your project and are dynamically loading
	// Steamworks SDK methods from dll/so, you can use the following method:
	// - SteamAPI_InitFlat()

[Thelvaen]

Removed:

• steam_api_init_ex(),
• init(),
• init_app(),

Replaced them with the call chain to SteamAPI_InitFlat()