The search for a matching importer had a few issues, see #3791. There were two different mechanisms to determine whether an importer accepts a specific file extension:
1. `aiImporterDesc::mFileExtensions`, which was forwarded to the UI via `BaseImporter::GetExtensionList()`.
2. `BaseImporter::CanRead()` when called with `checkSig == false`, which determines whether to actually use that importer.
Both were redundant and got out of sync repeatedly. I removed 2. completely and replaced it with 1., thereby syncing UI/import and shortening all `BaseImporter::CanRead()` implementations.
Further bugfixes:
- fixed glTF2 importer throwing exceptions when checking whether it can load a file
- removed `BaseImporter::SimpleExtensionCheck()` because it is no longer used and had a bug with case sensitivity
Since the `checkSig` parameter in `BaseImporter::CanRead()` is now useless, it can be removed completely. I’m not sure if this would break ABI compatiblity, so I’ll submit it with a later pull request.
“LazyDictBase::WriteObjects()” in the two glTF implementations is only used for export. Since it’s a virtual method, and many compilers have trouble removing unreferenced virtual methods, glTF export stuff is pulled into the binary even if compiling without exports.
This commit removes said virtual function if only compiling for import.
This removes 75 KiB of useless code when compiled with Visual Studio for x64.