lsteamclient: Fix count in wow64 networking messages conversion.

[viper9503]

Fix count in WOW64 networking messages conversion

Problem

Multiplayer is broken for 32-bit games running on 64-bit systems (the WOW64 path). Stardew Valley is the most commonly reported case, players can't join or host multiplayer sessions on Proton 10.0, but it works fine on 9.0-4.

The WOW64 overloads of receive_messages_utow and send_messages_wtou in lsteamclient/unix_steam_networking_manual.cpp use while(count--) to copy ptr32<> pointer arrays into native 64-bit arrays. Since count is uint32_t, the post-decrement wraps it to UINT32_MAX after the loop. The subsequent call to the actual message processing function receives this corrupted count, so networking messages are never delivered.

Affected games

Any 32-bit game that uses Steam networking APIs for multiplayer, including:

• Stardew Valley (AppID 322170)
• Other 32-bit titles using ISteamNetworkingSockets or ISteamNetworkingMessages

64-bit games are unaffected as they don't use the ptr32<> code path.

Fix

Replace while(count--) with for(i = 0; i < count; ++i) in all three WOW64 thunk functions so count is preserved for the subsequent call.