Add missing standard library includes for self-sufficient headers

Fixes builds with newer GCC/libstdc++ that no longer provide <cstdint>,
<cstring>, <cfloat>, <memory>, <algorithm> etc. transitively. Also
disambiguates visit<> calls in taxonomy.h with the full namespace and
casts the character value in IfcCharacterDecoder to uint32_t to silence
ambiguous overload warnings.

src/serializers/RocksDbSerializer.cpp

@@ -4,6 +4,9 @@
 
 #include <rocksdb/options.h>
 
+#include <cstdint>
+#include <cstring>
+
 #include "../ifcparse/IfcLogger.h"
 
 RocksDbSerializer::RocksDbSerializer(IfcParse::IfcFile* file, const std::string& rocksdb_filename)