Ruby » Ruby master

merge revision(s) 49482,49487: [Backport #10821]

    * lib/mkmf.rb (try_cppflags, try_cflags, try_ldflags): get rid of
      interference by modifying global variables in have_devel? method.
      [ruby-core:67962] [Bug #10821]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@49735 b2dd03c8-39d4-4d8f-98ff-823fe69b080e