man: generate configured paths in manpages

In particular, use /lib/systemd instead of /usr/lib/systemd in distributions
like Debian which still have not adopted a /usr merge setup.

Use XML entities from man/custom-entities.ent to replace configured paths while
doing XSLT processing of the original XML files. There was precedent of some
files (such as systemd.generator.xml) which were already using this approach.

This addresses most of the (manual) fixes from this patch:
http://anonscm.debian.org/cgit/pkg-systemd/systemd.git/tree/debian/patches/Fix-paths-in-man-pages.patch?h=experimental-220

The idea of using generic XML entities was presented here:
http://lists.freedesktop.org/archives/systemd-devel/2015-May/032240.html

This patch solves almost all the issues, with the exception of:
- Path to /bin/mount and /bin/umount.
- Generic statements about preference of /lib over /etc.

These will be handled separately by follow up patches.

Tested:
- With default configure settings, ran "make install" to two separate
  directories and compared the output to confirm they matched exactly.
- Used a set of configure flags including $CONFFLAGS from Debian:
  http://anonscm.debian.org/cgit/pkg-systemd/systemd.git/tree/debian/rules
  Installed the tree and confirmed the paths use /lib/systemd instead of
  /usr/lib/systemd and that no other unexpected differences exist.
- Confirmed that `make distcheck` still passes.

1 files changed, 6 insertions, 3 deletions

diff --git a/man/hwdb.xml b/man/hwdb.xml
index 509dab81c5..b3602ac5da 100644
--- a/man/hwdb.xml
+++ b/man/hwdb.xml
@@ -1,6 +1,9 @@
 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
-  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+<!ENTITY % entities SYSTEM "custom-entities.ent" >
+%entities;
+]>
 
 <refentry id="hwdb" conditional="ENABLE_HWDB">
   <refentryinfo>
@@ -40,7 +43,7 @@
 
   <refsect1><title>Hardware Database Files</title>
       <para>The hwdb files are read from the files located in the
-      system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename>,
+      system hwdb directory <filename>&udevlibexecdir;/hwdb.d</filename>,
       the volatile runtime directory <filename>/run/udev/hwdb.d</filename>
       and the local administration directory <filename>/etc/udev/hwdb.d</filename>.
       All hwdb files are collectively sorted and processed in lexical order,
@@ -70,7 +73,7 @@
       <para>The content of all hwdb files is read by
       <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
       and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
-      or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the compiled
+      or alternatively <filename>&udevlibexecdir;/hwdb.bin</filename> if you want ship the compiled
       database in an immutable image.
       During runtime only the binary database is used.</para>
   </refsect1>