Fix MSVC streamer template instantiation

Export the explicit full-buffer instantiation instead of the generic class. MSVC otherwise emits a default-constructor closure for the paged reader, instantiating an unsupported constructor.

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src/ifcparse/file.h

@@ -91,7 +91,7 @@ enum filetype {
 IFC_PARSE_API filetype guess_file_type(const std::string& path);
 
 template <typename Reader = file_reader<full_buffer_impl>>
-class IFC_PARSE_API instance_streamer {
+class instance_streamer {
 private:
     std::unique_ptr<Reader> owned_stream_;
     Reader* stream_;