Fix handling data which contains surrogate pair characters when using "fmalt" for FileMaker Server 11 or earlier

This pull request fixes handling data which contains surrogate pair characters when using "fmalt". (Modify RetrieveFM7Data.class.php.)
And consider the version of FileMaker Server when using "fmalt", too (FileMaker Server 7-11 need the surrogate pair patch of FX.php, but FileMaker Server 12 doesn't require the surrogate pair patch).