Added a parsetree argument for parsing IRIs.

* [DCG_MULTI,FIX] Removed determinism.
* [RFC3987_DCG,EXT] Added parsetree argument.
* [RFC3987_DCG,DOC] Added documentation.
* [RFC4234,RFC2616_BASIC,EXT] Include code argument in 'DIGIT'//2.
* [RFC4234,FIX] Removed duplicate clasue 'ALPHA'//1.