Add a conditional entity for sysv/systemd

This removes the need for versiond, and other xxxd entities. Those
entities will be removed in the next commits.

general.ent

@@ -1,28 +1,39 @@
+<!-- Automatically generated by git-version.sh -->
+<!ENTITY % conditional-entities SYSTEM "conditional.ent">
+%conditional-entities;
+
 <!-- version info automatically generated by git
-     comment the following two lines for release -->
+     comment out the following two lines for release -->
 <!ENTITY % version-entities SYSTEM "version.ent">
 %version-entities;
 
 <!-- uncomment and edit the following four lines
      for releases (including -rc) -->
 <!--
+<![ %sysv; [
 <!ENTITY version         "10.2-rc1">
-<!ENTITY versiond        "10.2-systemd-rc1">
+]]>
+<![ %systemd; [
+<!ENTITY version         "10.2-systemd-rc1">
+]]>
 <!ENTITY releasedate     "August 26th, 2021">
 <!ENTITY copyrightdate   "1999-2021">
 -->
 
-<!ENTITY short-version   "svn">  <!-- Used below in &blfs-book;
+<![ %sysv; [
+<!ENTITY short-version   "svn">  <!-- Used below in &blfs-book; 
                                       Change to x.y for release but not -rc releases -->
 <!ENTITY generic-version "development"> <!-- Use "development"  or "x.y[-pre{x}]" -->
-
-<!ENTITY short-versiond  "systemd">  <!--Change to stable-systemd for release  -->
-<!ENTITY generic-versiond "systemd">
+]]>
+<![ %systemd; [
+<!ENTITY short-version  "systemd">  <!--Change to stable-systemd for release  -->
+<!ENTITY generic-version "systemd"> 
+]]>
 
 <!ENTITY lfs-root        "https://www.linuxfromscratch.org/">
 <!ENTITY blfs-root       "&lfs-root;blfs/">
 <!ENTITY blfs-book       "&blfs-root;view/&short-version;/">
-<!ENTITY blfs-systemd-book "&blfs-root;view/&short-versiond;/">
+<!ENTITY blfs-book       "&blfs-root;view/&short-version;/">
 <!ENTITY faq-root        "&lfs-root;faq/">
 <!ENTITY hints-root      "&lfs-root;hints/downloads/files/">
 <!ENTITY hints-index     "&lfs-root;hints/list.html">
@@ -33,12 +44,12 @@
 <!ENTITY errata          "&lfs-root;lfs/errata/&generic-version;/">
 <!ENTITY secadv          "&lfs-root;lfs/advisories/">
 <!ENTITY min-kernel      "3.2">
-
+<!--
 <!ENTITY patches-rootd   "&lfs-root;patches/lfs/&generic-versiond;/">
 <!ENTITY downloads-rootd "&lfs-root;lfs/downloads/&generic-versiond;/">
 <!ENTITY test-resultsd   "&lfs-root;lfs/build-logs/&generic-versiond;/">
 <!ENTITY erratad         "&lfs-root;lfs/errata/&generic-versiond;/">
-
+-->
 <!ENTITY lfs-ticket-root "https://wiki.linuxfromscratch.org/lfs/ticket/">
 
 <!ENTITY anduin-sources  "https://anduin.linuxfromscratch.org/LFS">