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/ifcparse/IfcFile.h

@@ -34,6 +34,7 @@
 #include <boost/circular_buffer.hpp>
 #include <iterator>
 #include <map>
+#include <cstdint>
 
 #ifdef IFOPSH_WITH_ROCKSDB
 #include <rocksdb/merge_operator.h>