* module/ice-9/peg/using-parsers.scm (prec): Use SRFI-9 to define PEG
record types.
(peg:start, peg:end, peg:string, peg:tree, peg:substring): Implement
in a more efficient way.
* module/ice-9/peg.scm: rename 'peg-sexp-compile' to
'compile-peg-pattern'
* module/ice-9/peg/codegen.scm: same
* module/ice-9/peg/string-peg.scm: same
* module/ice-9/peg/using-parsers.scm: same
* doc/ref/api-peg.texi: same
* module/ice-9/peg.scm: rename 'define-nonterm' to 'define-peg-pattern'
* module/ice-9/peg/using-parsers.scm: same
* module/ice-9/peg/string-peg.scm: same
* test-suite/tests/peg.test: same
* doc/ref/api-peg.texi: same
* module/ice-9/peg.scm: rename 'peg-parse' to 'match-pattern'
* module/ice-9/peg/string-peg.scm: same
* module/ice-9/peg/using-parsers.scm: same
* doc/ref/api-peg.texi: same
* test-suite/tests/peg.test: same
* test-suite/tests/peg.bench: same
* doc/ref/api-peg.texi: rename 'peg-match' to 'search-for-pattern'
* module/ice-9/peg.scm: same
* module/ice-9/peg/using-parsers.scm: same
* test-suite/tests/peg.test: same
* 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
