[Spitbol] Added the last features from peg.parsers

- arbg, arbnog : same as arb and arbno, but being greedy
- repeat0, repeat1 (repeat0 is arbnog, and repeat1 is derived from it,
  which makes same more supple than their peg.parsers counterparts)
- 'digit', 'integer', 'string'
- from-m-to-n
- pack, surrounded-by, list-of
+ parse-nostart which implements Spitbol patterns matching starting from
any position in the string
The resulting AST's structure appears to still be unsatisfactory in
certain cases (as exposed by list-of)