1. DCG grammar for IRIs.
2. Consolidation of the XML and SVG codebase.

* [DCG_CARDINAL,NEW] Added between_digit//4 for easily processing digits that belong to a given range.
* [DCG_CONTENT,NEW] Added between//3 and between_hex//3 fir easily processing character codes within a certain (decimal or hexadecimal) range.
* [DCG_CALLS,NEW] Added dcg_calls//2 for executing a given list of DCG rules with the given separator DCG rule processed in between the occurrences.
* [RFC3987,NEW] New module implementing the DCG for IRIs.
* [XSD_DATETIME,SC] Simplified code using the new between_digit//4.