Logs a notification instead of silently dropping long log messages, which can complicate debugging.
This way, if you don't see a message you expect to see, you'll immediately know why.
The *correct* approach would be to eliminate length filtering here entirely and use `snprintf` appropriately (also there's a tiny -- probably negligible -- performance hit here in calling `strlen` regardless of whether or not the verbosity level matches). Failing that, the second best option is to copy and truncate messages here. However, for now, this should be OK.
- GetImporterInstanceList reads ASSIMP_ENABLE_DEV_IMPORTERS env var. Development importers are enabled if the env var is set and is not equal to the literal string "0".
- X3D importer will not be registered unless ASSIMP_ENABLE_DEV_IMPORTERS is set; addresses #3647.
TODO: If this change is incorporated, it should be documented.
NOTE: Effective git branch structure is a better solution. This is an alternate for #3825.
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.
