* [MATH,SC] Split MATH_EXT into several modules: FLOAT_EXT, RATIONAL_EXT, INT_EXT, RANDOM_EXT.
* [MATH,NEW] Implemented mod/3 and div/3 for floats and rationals.
* [RDF_CLEAN,EXT] Rewrote rdf_convert_datatype/6 using the new XSD implementation.
* [XSD,NEW] Added xsd_convert_datatype/4.
* [XSD_DECIMAL,FIX] Various fixes to lexical and canonical mapping. Seems to work now...
* [XML_SCHEMA_DATATYPES,SC] Completely removed.
* [XMLS_DATETIME,SC] Removed sign//2 (already in DEC_CARDINAL).