merge revision(s) 39525: [Backport #8102]

	configure.in: escape double-quotes

	* configure.in (unexpand_shvar): escape double-quotes in backquotes in
  double-quotes for some shells.  [Bug #7959]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39825 b2dd03c8-39d4-4d8f-98ff-823fe69b080e