INSTALL: add warning on docbook-xsl 1.72 and 1.73

Signed-off-by: Junio C Hamano <gitster@pobox.com>

INSTALL

@@ -116,3 +116,7 @@ Issues of note:
    would instead give you a copy of what you see at:
 
 	http://www.kernel.org/pub/software/scm/git/docs/
+
+   It has been reported that docbook-xsl version 1.72 and 1.73 are
+   buggy; 1.72 misformats manual pages for callouts, and 1.73 needs
+   the patch in contrib/patches/docbook-xsl-manpages-charmap.patch

contrib/patches/docbook-xsl-manpages-charmap.patch

@@ -0,0 +1,21 @@
+From: Ismail Dönmez <ismail@pardus.org.tr>
+
+Trying to build the documentation with docbook-xsl 1.73 may result in
+the following error.  This patch fixes it.
+
+$ xmlto -m callouts.xsl man git-add.xml
+runtime error: file
+file:///usr/share/sgml/docbook/xsl-stylesheets-1.73.0/manpages/other.xsl line
+129 element call-template
+The called template 'read-character-map' was not found.
+
+--- docbook-xsl-1.73.0/manpages/docbook.xsl.manpages-charmap	2007-07-23 16:24:23.000000000 +0100
++++ docbook-xsl-1.73.0/manpages/docbook.xsl	2007-07-23 16:25:16.000000000 +0100
+@@ -37,6 +37,7 @@
+   <xsl:include href="lists.xsl"/>
+   <xsl:include href="endnotes.xsl"/>
+   <xsl:include href="table.xsl"/>
++  <xsl:include href="../common/charmap.xsl"/>
+
+   <!-- * we rename the following just to avoid using params with "man" -->
+   <!-- * prefixes in the table.xsl stylesheet (because that stylesheet -->