Update URL to unicode.org's FTP site using an HTTP URL to the same

document.

Doc/lib/libunicodedata.tex

@@ -18,7 +18,7 @@ this database is based on the \file{UnicodeData.txt} file version
 
 The module uses the same names and symbols as defined by the
 UnicodeData File Format 3.0.0 (see
-\url{ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.html}).  It
+\url{http://www.unicode.org/Public/UNIDATA/UnicodeData.html}).  It
 defines the following functions:
 
 \begin{funcdesc}{decimal}{unichr\optional{, default}}