Adapted to new field Production p in production constructor of
AbstractValue
Addition to/fixes in MuPrimitives

- mint now accepts Java integers and PDB integers
- added regexp primitives:
  regexp_begin: give begin of matched region
  regexp_end: give end of matched region
  regexp_set_region: restrict match to a region
- added size_str (and added a case to size as well
- added substring primitives:
  substring_str_mint_mint
  is_tail_str_str_mint
Extended the muRascal library for string visits.

- Dcoumented and extended the handling of visits
- Added MATCH_SUBSTRING for matching strings during visits
- Added MATCH_REGEXP_IN_VISIT
- Added VISIT_STR

Minor:
- fixed typo in ENUM_NODE (iter-start-seps => iter-star-seps)
Added support for string visits
Reorganization of grammar reification (work in progress)

Changes in the type checker force changes at the compiler side.
This is in flux and related tests are curently failing.
Merge branch 'master' of https://github.com/cwi-swat/rascal.git