Merge pull request #84 from jubalh/mentionman

Add note about conditional man pages

man/README.md

@@ -0,0 +1,10 @@
+The [official releases](https://github.com/shadow-maint/shadow/releases) ship
+with pre-built manpages.
+
+The content of the man pages however is dependent on compile flags. So the
+pre-built ones might not fit your version of shadow.  To build them yourself use
+`--enable-man`. Furthermore the following build requirements will be needed:
+- xsltproc
+- docbook 4
+- docbook stylesheets
+- xml2po