zlib.c: replace with substring
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57042 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
zlib.c: replace with substring
portion substring, not modifying the input buffer directly.
[ruby-core:78567] [Bug #13021]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57042 b2dd03c8-39d4-4d8f-98ff-823fe69b080e