* module/ice-9/peg.scm: move code out of here
* module/ice-9/peg/match-records.scm: remove this file
* module/ice-9/peg/using-parsers.scm: make a new module with utilities for
using parsers. It contains the code from both peg.scm and match-records.scm
* module/ice-9/peg/string-peg.scm: update to use new module
