* configure.in: fix to undefine HAVE_MEMEM collectlly if it is broken.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44920 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-02-13

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44921 b2dd03c8-39d4-4d8f-98ff-823fe69b080e