merge revision(s) d0ba4abf1a00339ebbb5d405db3240a8bdb7b68b,54eac83b2ad77ddea84fa6d66c09e0bb014cf61e: [Backport #15786]
Add RB_ID_SERIAL_MAX Hide internal IDs * parse.y (internal_id): number the ID serial for internal use by counting down from the neary maximum value, not to accidentally match permanent IDs. [Bug #15768]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67758 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) d0ba4abf1a00339ebbb5d405db3240a8bdb7b68b,54eac83b2ad77ddea84fa6d66c09e0bb014cf61e: [Backport #15786]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67758 b2dd03c8-39d4-4d8f-98ff-823fe69b080e