Allow man pages to link to each other

doc/asciidoc.conf

 # Copyright 2015 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 11 matching lines @@
 # revision is desirable, so change this to use revdate, an attribute that can be
 # computed and passed in by the script that runs AsciiDoc. For man pages, use
 # the mansource and manversion attributes instead of the hard-coded “Version”
 # string and revnumber attribute, so that the version will appear as “Crashpad
 # 0.7.0” as it does in “man” output.
 ifdef::basebackend-html[]
 [footer-text]
 {mansource=Version} {manversion={revnumber}}{basebackend-xhtml11?<br />}{basebackend-xhtml11=<br>}
 Last updated {revdate}
 endif::basebackend-html[]
+
+# The man_link macro was inspired by git’s linkgit macro. See
+# https://github.com/git/git/blob/master/Documentation/asciidoc.conf.
+ifdef::doctype-manpage[]
+
+[macros]
+(?su)[\\]?(?P<name>man_link):(?P<target>\S*?)\[(?P<attrlist>.*?)\]=
+
+ifdef::backend-docbook[]
+[man_link-inlinemacro]
+{0%{target}}
+{0#<citerefentry>}
+{0#<refentrytitle>{target}</refentrytitle><manvolnum>{0}</manvolnum>}
+{0#</citerefentry>}
+endif::backend-docbook[]
+
+ifdef::basebackend-html[]
+[man_link-inlinemacro]
+<a href="{target}.html">{target}{0?({0})}</a>
+endif::basebackend-html[]
+
+endif::doctype-manpage[]