* ext/tk/extconf.rb: Default search_versions are set 8.5 and 8.4 only. At present, Tcl/Tk8.6 is not supported.
* ext/tk/extconf.rb: Fix typo. [ruby-core:56084] [Bug #8656]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42059 b2dd03c8-39d4-4d8f-98ff-823fe69b080e