Add a proper class for dealing with fallback models and the warnings thereof. Also reverted the 'old_gather_props' removal, as otherwise fallback models won't draw (new gather props solution doesn't call CMDLCache::GetHardwareData()).
Rebuild 'CMDLCache::GetPhysicsGeometry()' and properly handle missing cache pointers. Also cleaned up various methods in CMDLCache and renamed 'studiophysicscache_t' to 'studiophysicsref_t'. The changes made the 'old_gather_props' convar hack redundant and has thus been removed.
Originally, we store the search results in a CMemory instance which we then assign to the actual function pointer. CMemory is just a pointer class; we can assign the results directly to the actual function pointer. This commit reduces a lot of code verbosity, and also reduced roughly 2KiB worth of static pointers in the resulting executable. This commit also officially deprecates the support for any GameDLL's below S3 (Season 3), since it makes more sense to port the assets from earlier/later games back to the version this SDK supports.
Utilize the new IDetour::DetourSetup() code, IDetour::Attach and IDetour::Detach have been removed in favor of this (significantly reduces chance of user error). Since the template check happens in the idetour header, it is much more aggressive on type mismatches, such as a difference in parameter types, between the function and detour, will now raise a compile time error. As a result, some type mismatches have been fixed in this commit as well.
