instead of Bison or byacc.

* parse.y: If OLD_YACC is defined, ensure that YYMAXDEPTH is at least
  10000 (Bison's default) since some old versions of Yacc define it as
  low as 150 by default, which is too low for Ruby to parse some files,
  such as date/format.rb.  Among other issues, the parse problem causes
  "make test" to fail.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@5093 b2dd03c8-39d4-4d8f-98ff-823fe69b080e